Module 1

What Is Search?

Search is the act of finding the right information out of everything you have, given a question. You type “car repair” into a box, and something has to decide which of your thousands of documents, products, or messages actually answers that.

Every search system, no matter how it’s built internally, does the same two things:

1. Retrieve: narrow a huge collection down to a shortlist of documents that might be relevant.
2. Rank: order that shortlist so the best answer ends up near the top.

At the heart of search is one question: what makes a result relevant? We’ll start with the simplest possible answer, watch it fail, and build up from there. No prior knowledge of vector search engines or indexing algorithms is assumed.