A NIST-run conference for testing how well search systems retrieve text.
TREC is a school quiz bowl for search engines. Everyone gets the same questions, so no one brags about an easy sheet.
It gives standard test sets for retrieval. People use them to judge search. They also use them for QA and RAG.
IR
TREC gives IR shared tasks and data for fair testing.
BM25
BM25 is often used as a baseline on TREC data.
QA
TREC's QA track helped shape open-domain QA testing.