They respond to prompts, scan through their data and give answers based on what their programming for probability dictates.
Humans seem to do the same thing much of the time but beneath even the most half-baked human reasoning is a self-directed sense of the world that no LLM has. The AI woo on HN is quite strong, so many will probably disagree for all kinds of shallow reasons of semantics, but even the creators of LLMs don't claim they possess anything resembling consciousness, which is necessary for understanding notions of truth and falsehood.