That’s an interesting rhetorical trick, because answering the question “what is an LLM” requires a lecture series, not a hacker news comment.

Compression schemes take an item, reduce it in size, and return the same item (lossy or lossless) when asked.

LLM's and other generative AI are not designed nor are particularly good at this. What they are good at is returning new results using 'learning' it has developed via training.

If I want to send someone a sample of code, I'll use zip. If I want to generate code from a prompt, I'll use a llm.