Semantic Search
Search that works on meaning rather than exact words, so a page can match a query it never literally contains. It is why writing naturally now beats repeating a keyword.
Related terms
Passage Ranking
When a search engine surfaces one relevant passage from a long page rather than judging the page as a whole. Clear headings are what make a passage findable in isolation.
Unsupervised Learning
Training a model on unlabelled data and letting it find structure by itself — grouping similar customers, say, without being told what the groups are.
RAG (Retrieval-Augmented Generation)
A technique where the AI first searches a set of documents, then writes its answer from what it found. It is how assistants quote current information rather than whatever was in their training data.
LLM (Large Language Model)
The kind of AI behind ChatGPT, Claude and Gemini. It is trained on an enormous amount of text and predicts what should come next, which is enough to answer questions, summarise, translate and write.
Guardrails
The limits placed on what an AI may say or do — refusing certain requests, staying on topic, never inventing a price. Essential on anything customer-facing.
Recommendation Engine
A system that suggests what somebody might want next based on behaviour — the “customers also bought” of an online shop. One of the oldest commercial uses of machine learning.