An AI system trained on huge amounts of text so it can understand language and write text, code and answers.
A large language model is a program trained on an enormous amount of text, learning the patterns of language and how words and ideas connect. When you send it a question or instruction, it predicts the most fitting response one token at a time. That is how it can draft a marketing message, summarize a document or write working code.
In an app, the LLM is the brain behind chat assistants, automated support and smart summaries. In builders like the Fanann Agent it also plans the app and writes the code. But it does not automatically know your private data, and it can be confidently wrong, so it needs clear context and review.
Practical tip: never treat the model as an absolute source of truth. Put the facts it needs directly in the request, tell it to say it does not know when the answer is missing, and test it on real questions from your customers before you launch.