A search method for ranking documents by keyword match.
BM25 is like hunting for fries in a school cafeteria. The short “FRIES” sign beats a giant salad poster.
Search and knowledge bases use it. It finds likely text first. Then the model answers from that text.
IR
BM25 is a classic ranking method in IR.
RAG
RAG often uses BM25 to find text before the model answers.
Vector search
BM25 pairs with Vector search for word match and meaning match.