In this article, we will understand how vector search works in Azure AI Search and how to use it as the retrieval layer in a Retrieval-Augmented Generation (RAG) system. The article is meant for software engineers. We will not stop at theory. We will build a small, working example that you can run on your own machine and follow along step by step. By the end, you will have a small document search service that takes a user question, finds the most relevant text using vector similarity, and prepares the context that you can pass to a language model.