Generative engine optimization, GEO, is the practice of making content easy for an AI assistant to fetch and use directly in an answer, rather than optimizing for a ranked position among ten blue links. Classic search ranks pages for a reader to click through; an assistant fetches material once, reads it, and hands back an answer with no click at all.
llms.txt is one narrow, unproven answer to that goal. Independent studies
find no measurable ranking benefit from publishing one, and Google's own
documentation says the same.
For what the evidence actually shows and why Birta still publishes one anyway, see what is an llms.txt file, a real one explained line by line.