A web crawler, also known as a spider or bot, functions as an automated script that systematically browses the internet to index content. Its primary role is to collect data from web pages to facilitate search engine indexing, enabling users to retrieve relevant information during searches. Crawlers analyze page content, follow hyperlinks, and update indexes with fresh data to improve search results. Efficient crawling ensures that an extensive array of web content is accessible, which is critical for enhancing the overall search experience for users across various search engines.