Search engines index website content through a process that includes crawling, indexing, and ranking. Crawling involves automated bots, or spiders, that explore web pages by following links to gather information. Once a page is crawled, the search engine analyzes its content, which is then organized into an index, allowing it to quickly retrieve relevant results. Ranking algorithms evaluate various factors such as relevance and authority to present the most pertinent content to users based on their search queries, ensuring efficient information retrieval.