Marketing and AI, defined plainly.
Practical definitions for the terms that come up across advertising, SEO, AI engineering, and analytics — each one short, honest, and linked to the tools and writing that go deeper.
AI engineering08
- Agentic AIAgentic AI describes systems where a language model runs in a loop — choosing actions, calling tools, and observing results — to pursue a goal, rather than answering in a single pass.
- Context windowThe context window is the maximum number of tokens a language model can consider at once — the combined size of the prompt and the response it generates.
- Model Context Protocol (MCP)MCP is an open protocol that standardizes how AI applications connect to external tools and data sources, so a model can use many integrations through one common interface.
- Prompt cachingPrompt caching stores the processed form of a stable prompt prefix so that repeated requests reusing it are billed at a steep discount and processed faster.
- Prompt engineeringPrompt engineering is the practice of structuring the input to a language model — instructions, examples, context, and format — to get more reliable and useful outputs.
- Retrieval-augmented generation (RAG)RAG is a technique that retrieves relevant documents at query time and feeds them to a language model as context, so answers are grounded in specific source material rather than only the model's training.
- Tokens (LLM)Tokens are the units a language model reads and generates — usually words, word-pieces, or punctuation, with leading spaces attached — and are the basis for both context limits and billing.
- Vector databaseA vector database stores data as high-dimensional embeddings and retrieves items by similarity, making it the search layer behind most retrieval-augmented AI systems.
SEO & AI search06
- Canonical tagA canonical tag tells search engines which URL is the preferred version of a page when the same or similar content is reachable at multiple addresses.
- Core Web VitalsCore Web Vitals are a set of Google metrics measuring real-world loading, interactivity, and visual stability, used as a signal in ranking.
- Generative engine optimization (GEO)GEO is the practice of making content more likely to be surfaced and cited by AI answer engines like ChatGPT, Google AI Overviews, and Perplexity.
- HreflangHreflang is an annotation that tells search engines which language and region a page targets, so the right version is shown to the right audience.
- Keyword difficultyKeyword difficulty is an estimated score of how hard it would be to rank on the first page for a search term, based mainly on the strength of the pages already ranking.
- llms.txtllms.txt is a proposed convention for a markdown file at a site's root that gives AI systems a curated, token-efficient map of the site's most useful content.
Paid advertising05
- CPC (cost per click)CPC is the average cost of a single click on an ad, calculated as spend divided by clicks.
- CPM (cost per mille)CPM is the cost of one thousand ad impressions, calculated as spend divided by impressions times 1,000 — the base unit for pricing reach.
- CTR (click-through rate)CTR is the share of impressions that resulted in a click, calculated as clicks divided by impressions.
- Quality ScoreQuality Score is a search-advertising diagnostic estimating the quality of your ads, keywords, and landing pages, which influences ad rank and the price you pay per click.
- ROAS (return on ad spend)ROAS is revenue attributed to advertising divided by the amount spent on it — a measure of how much revenue each unit of ad spend returned.
Marketing analytics07
- AttributionAttribution is the practice of assigning credit for a conversion to the marketing touchpoints that preceded it, using a chosen rule such as last-click, first-click, or a multi-touch model.
- Conversion rateConversion rate is the share of visitors or clicks that completed a desired action, calculated as conversions divided by the total.
- Customer acquisition cost (CAC)CAC is the average cost to acquire one customer, calculated as total acquisition spend divided by the number of customers gained.
- Customer lifetime value (LTV)LTV is the total gross profit a customer is expected to generate over their relationship with a business, used to judge how much can be spent to acquire them.
- IncrementalityIncrementality is the portion of conversions that advertising actually caused, as opposed to conversions that would have happened without it, measured by holding out a randomized control group.
- Statistical significanceA result is statistically significant when the observed difference would be unlikely to occur by chance if there were truly no effect — conventionally, a probability below 5%.
- UTM parametersUTM parameters are tags added to a URL — source, medium, campaign, and more — that let analytics tools attribute a visit to a specific marketing effort.
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