Fifty-seven terms across seven families. Each one says what it means, when it matters to you, and what it usually costs when two people read it differently.
Short answer
Most bad project decisions start as a word two people understood differently. This glossary defines the fifty-seven terms that show up in software, marketing, AI and event proposals, one sentence each, in the sense a buyer needs rather than the sense a textbook gives. Where a term regularly costs someone money, that is written down too.
Agencies and vendors are fluent in this vocabulary and clients usually are not. That asymmetry is where scope creep, surprise invoices and disappointing launches live.
So this page is deliberately blunt. Each entry says what the term means, when it matters to you, and where it tends to be used to obscure rather than explain.
The seven numbers every proposal quietly argues about.
What one customer costs to win, and what that customer brings back. Everything else is a rounding error.
Matters whenDeciding whether to spend more on traffic or fix the product first.
Watch forIf the two numbers do not converge, more traffic only makes the loss bigger.
Customer acquisition cost. Everything spent on marketing and sales in a period, divided by the customers won in it.
Matters whenSetting a ceiling on what a click, a lead or a demo is allowed to cost.
Lifetime value. The gross profit one customer brings before they stop buying.
Matters whenWorking out how much you can afford to pay for a customer without going broke.
How many months of gross profit it takes to earn back what you spent winning that customer.
Matters whenJudging whether growth funds itself or eats the bank balance.
Watch forUnder twelve months is survivable. Past eighteen, you are financing your own marketing.
Revenue minus the direct cost of delivering it. Not revenue, and not net profit.
Watch forBudgets set as a share of revenue instead of margin overspend by exactly the cost of goods.
Monthly recurring revenue. Subscription income that renews without a new sale.
Matters whenAny product with a plan, a seat or a licence rather than one-off invoices.
How many months the company can keep operating at today's burn before the money is gone.
The words that decide who pays when something changes.
One number agreed before work starts, covering a scope written down in the same document.
Matters whenBuyers who need a budget approved before the first line of code.
Watch forA fixed price with a vague scope is not a price. It is an argument scheduled for later.
The written list of what is included, and just as importantly, what is not.
Watch forMost project disputes are not about quality. They are about a sentence nobody wrote down.
A short paid phase that turns a rough idea into a scope, a timeline and a price you can sign.
Matters whenProjects where the brief is still a conversation rather than a document.
A named point in the plan where something works, gets shown, and gets paid for.
Matters whenSplitting risk so neither side is ever more than one milestone out of pocket.
A written amendment when the scope moves, with its own price and its own effect on the date.
Watch forWithout one, changes are absorbed silently until the timeline slips and nobody can say why.
The moment code, accounts, domains and documentation move into your control.
Matters whenAny agency relationship you might one day leave.
Watch forAsk what the handover contains before you sign, not after the relationship sours.
Service level agreement. A promise about response time and uptime, with a consequence attached.
Matters whenAnything that costs money per hour while it is down.
What gets built, and the shapes it comes in.
The smallest version a real user can complete a real task in. Not a demo, and not a prototype.
Matters whenTesting whether anyone wants the thing before building all of it.
Watch forAn MVP that skips payments, onboarding or support is not minimal. It is unfinished.
Software that runs in a browser with no install, reachable from any device with a link.
A web app that installs to the home screen, works offline and sends push notifications.
Matters whenReaching phones without paying the app store tax or waiting on review.
A web app that opens inside Telegram, already knowing who the user is.
Matters whenAudiences that live in a chat and will not install anything else.
A defined way for one system to ask another for data or actions, with no human in between.
Connecting two systems so a fact entered once appears in both.
Matters whenKilling the spreadsheet somebody rekeys every morning.
A message one system pushes to another the moment something happens, instead of being asked every minute.
The system of record for who your customers are and what has been said to them.
Matters whenAny sales process with more than one person answering.
A full copy of the live system where changes are tested before real users see them.
Watch forA project without staging tests in production, whether or not anyone admits it.
Shortcuts taken to ship faster, which later charge interest in the form of slower changes.
Watch forDebt is a tool, not a sin. Unmeasured debt is the problem.
The vocabulary behind every AI quote you will be sent this year.
Large language model. A model trained to predict text, which is why it can write, summarise and classify.
The instruction given to a model. In production it is a versioned asset, not a message typed once.
Matters whenAnywhere output quality has to stay stable across thousands of runs.
How much text a model can hold in view at once, counting the question and the answer together.
Watch forLong documents do not fail loudly when they exceed it. They quietly lose the middle.
The unit models are billed and measured in. Roughly three quarters of a word in English.
Matters whenEstimating what an AI feature will cost per user per month.
Retrieval augmented generation. The model answers from your documents, fetched at the moment of asking.
Matters whenSupport and internal search, where answers must come from your own material.
Watch forRAG fails on retrieval far more often than on generation. Budget the effort accordingly.
A model given tools and a goal, allowed to take several steps before returning an answer.
Matters whenMulti-step work like triage, research or filling a form from an email.
Watch forEvery tool an agent can call is an action it can take by mistake. Scope the permissions first.
Further training on your own examples, to fix tone and format rather than to add knowledge.
Watch forMost requests for fine-tuning are actually requests for retrieval, and cost ten times less as one.
A confident answer with no basis in the source material.
Watch forIt is a property of the technology, not a bug awaiting a patch. Design the workflow to survive it.
A checkpoint where a person approves or edits before the output reaches a customer or a ledger.
Matters whenAnything with money, legal exposure or a public audience attached.
A rule enforced outside the model: what it may not say, spend, send or delete.
How spend turns into demand, and how you tell whether it did.
Advertising bought against a measurable action rather than against reach or impressions.
Cost per lead. What you pay for one contact who raised a hand.
Watch forCheap leads that never buy are the most expensive thing in the funnel.
Cost per acquisition. What you pay for one completed sale or signup.
Return on ad spend. Revenue divided by the spend that produced it.
Watch forROAS on revenue flatters every business with a real cost of goods. Judge it on margin.
Deciding which touch gets the credit when a customer saw six things before buying.
Watch forPlatforms each claim the same sale. The sum of their reports will exceed your bank statement.
The sequence from first contact to payment, measured as the share surviving each step.
Matters whenFinding the one step where most of the loss happens, before spending more at the top.
Advertising to people who already visited, which is why it always looks efficient.
Watch forIt harvests demand you already created. It does not create new demand.
The ad itself: the image, the video, the words.
Matters whenThe lever with the widest range of outcomes once targeting is set up.
A page built for one audience and one action, separate from the main site.
Being found by search engines, and now by the models people ask instead.
Making pages rank in search results through content, structure and links.
Generative engine optimisation. Making pages easy for AI assistants to quote correctly.
Matters whenCategories where buyers now ask a model before they open a search page.
Watch forAnswers get cited without a click. Measure mentions, not only sessions.
Machine-readable labels in the page saying what a thing is: an article, a price, a question.
Matters whenGetting quoted accurately instead of paraphrased loosely.
A plain text file at the site root pointing AI crawlers at the pages worth reading.
Matters whenSites whose value sits in documentation, offers or reference material.
The tag naming the one real address of a page when several URLs show the same thing.
Watch forDuplicates split ranking between copies rather than adding up.
The tag telling search engines which language version to show which visitor.
Matters whenAny site in more than one language.
Google's measurements of loading, responsiveness and layout stability, taken from real visitors.
The moving parts of a room full of people.
A paying or invited attendee, as distinct from a speaker, sponsor or staff member.
The minute-by-minute script of the event: who is where, what plays, who speaks next.
Matters whenAnything with a stage, a screen and more than two speakers.
Turning a registration into a badge at the door, fast enough that no queue forms.
Watch forCheck-in is where most events visibly fail. Test it at full speed before the day.
Letting sponsors capture the contacts they met, with consent, instead of collecting business cards.
Matters whenEvents where sponsors need to justify the spend afterwards.
A participant catalogue with a way to request a meeting, usually a bot or a mini app.
Matters whenConferences whose real product is who is in the room.
One event running live and online at once, with two different experiences to design.
Watch forA camera pointed at a stage is a recording, not a hybrid event.
What a sponsor actually does at the event, beyond a logo on a banner.
Matters whenSelling sponsorship a second year to the same company.
Take any quote you have been sent and mark every term from this page. Then check that the document says which meaning it intends.
Three questions settle most of it. What exactly is in scope. What happens, in writing, when the scope changes. And what you receive on the last day.
Anything specific to one country's regulation belongs in a lawyer's document, not in a vendor glossary. The same goes for jargon that exists only to make a deck sound expensive.
Where a term has a whole article behind it, the blog carries the long version. This page stays at one sentence each.
Because the alternative is explaining the same twenty words in every first conversation. A client who reads this arrives able to challenge our proposal, which produces a better scope than one who nods along.
Scope, by a wide margin. Almost every argument about quality or delay traces back to a sentence that was never written down, and both sides remember the conversation differently and honestly.
Ask for the cost per user per month at the expected volume, and ask what happens when the model is wrong. A vendor who cannot answer either has not built the thing before.
The work overlaps but the target differs. SEO competes for a position in a list. GEO competes to be the source a model quotes, which rewards clear answers, specific numbers and structured markup over keyword density.
Yes. Scope, milestone, change request and handover mean here exactly what they mean in our agreements, which is the point of writing them down publicly.