Google uses web crawlers to index the entire web and stores copies in its database. When a user searches, Google matches keywords to pages in its index and ranks results by relevance. Over time, Google has introduced many algorithm updates like Caffeine, Panda, Penguin, and Hummingbird to improve search quality and understand user intent rather than just keywords. With Hummingbird, Google focuses on concepts rather than words through features like the Knowledge Graph and natural language processing. Best practices for websites include optimizing titles, content, URLs, images and mobile formatting to be found by Google.