Web search

The core technology uses automated crawlers to index billions of web documents, delivering relevant results (SERPs) to a user's query in milliseconds.

Web search is an information retrieval system: its engine executes a multi-stage process involving a crawler, indexer, and database. The crawler (or bot) continuously discovers and analyzes web pages, while the indexer catalogs this massive data—a process that must scale to trillions of documents. When a user submits a query, the system rapidly consults this index, applying proprietary ranking algorithms (like Google’s PageRank) to deliver a prioritized list of hyperlinks. This technology is dominated by major players; Google Search alone commands approximately 90% of the worldwide market share, making it the de facto standard for accessing the global information space.

https://en.wikipedia.org/wiki/Web_search_engine