Training Data
Definition
The text that an AI model learned from before it was made available to the public — books, articles, websites, code, and other written material, totalling billions of words. The model doesn't "remember" any of it the way you remember reading a book. It absorbed patterns from it. What an AI knows, and the limits of what it knows, come from what was in that training data.
Why It Matters
It explains why AI tools sometimes know obscure things, sometimes miss obvious things, and have a knowledge cutoff date after which they don't know what happened in the world.
What does that look like in practice?
Ask why an AI knows an obscure 1800s poem but flubs last year's news, and the answer is in its training data.
What people actually mean when they say this
When someone says 'the AI learned it somewhere,' they mean it absorbed patterns from its training data, not that it remembers reading a specific page.
Last reviewed: March 2026
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