If you aren’t interested in learning how Google creates the index and the database of documents that it accesses when processing a query, skip this description. I adapted the following overview from Chris Sherman and Gary Price’s wonderful description of How Search Engines Work in Chapter 2 of The Invisible Web (CyberAge Books, 2001).

Google runs on a distributed network of thousands of low-cost computers and can therefore carry out fast parallel processing. Parallel processing is a method of computation in which many calculations can be performed simultaneously, significantly speeding up data processing. Google has three distinct parts:

Googlebot, a web crawler that finds and fetches web pages.
The indexer that sorts every word on every page and stores the resulting index of words in a huge database.
The query processor, which compares your search query to the index and recommends the documents that it considers most relevant.