How do web crawlers work?

We all know that Google is the most popular and widely used Search Engine therefore Google is the most popular web crawler at present which crawls millions of websites and billions of web pages every day.

The Internet has trillions of TB of data and when a user searches for something, they seek the most accurate information for that search query. Web Crawlers or Bots are responsible for crawling a website, categorizing, indexing, and showing the most accurate result for a search query that is relevant and appropriate.