This blog explains what a vector database is and how it stores vector embeddings to perform semantic similarity searches instead of traditional keyword matching. It describes how vector databases integrate with Large Language Models (LLMs) through Retrieval-Augmented Generation (RAG) to provide accurate, domain-specific, and up-to-date responses. The guide walks through the complete data pipeline, including document chunking, embedding generation, indexing with ANN algorithms, and similarity search. It also explains how user queries are converted into embeddings, matched against stored vectors, and used to retrieve relevant context for LLMs. Additionally, the article covers best practices, common challenges, and the limitations of vector databases in production AI systems. Finally, it compares popular vector databases such as pgvector, Pinecone, Qdrant, Weaviate, and Milvus to help readers choose the right solution for their AI applications.