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Understanding AI6 min16 June 2026

AI Glossary: 20 Terms Explained in Plain English

AI, LLM, prompt, hallucination, agent, token… The vocabulary of AI can feel like a foreign language. Here are 20 terms explained simply, one sentence each, so you never feel lost again.

The basics

  • AI (artificial intelligence): a program capable of performing tasks that normally require human intelligence.
  • Generative AI: an AI that creates content (text, images, audio) rather than simply classifying or predicting.
  • LLM (large language model): the engine behind ChatGPT and its peers, trained on massive amounts of text.
  • ChatGPT / Claude / Gemini / Le Chat: conversational assistants built on LLMs.

When you use it

  • Prompt: the message you write to an AI to ask it for something.
  • Token: a fragment of a word. AI reads and writes in tokens, not letters.
  • Context: everything the AI “keeps in mind” during the current conversation.
  • Hallucination: when an AI makes up false information and presents it as fact.
  • AI agent: an AI that does more than answer, chaining actions together to reach a goal.

Behind the scenes

  • Training: the phase where the model learns from data.
  • Training data: the texts and images the model learned from.
  • Model: the trained “brain” that you then use.
  • Open source: a model whose inner workings are public and reusable (Mistral offers some).
  • Multimodal: an AI that understands multiple formats (text + image + audio).

Where the debate is

  • Bias: prejudices present in the data, which the AI can reproduce.
  • Deepfake: fake content (voice, video) generated by AI, sometimes used in scams.
  • EU AI Act: the European regulation that governs how AI can be used.
  • GDPR: the European data protection rules, which apply to AI too.
  • Sovereignty: the idea of keeping control (and the data) on European soil.
  • Prompt injection: a technique for tricking an AI by slipping it hidden instructions.

What now?

Knowing the words is the first step to losing the fear. To put it into practice, test your reflexes with the free quiz, or learn how to write a good prompt. And to go further, our online courses guide you step by step.