Search engines “crawl” websites, going from one page to another incredibly quickly, acting like hyperactive speed-readers. They make copies of your pages that get stored in what’s called an “index,” which is like a massive book of the web.
Each site is given a crawl budget, an approximate amount of time or pages a search engine will crawl each day, based on the relative trust and authority of a site. Larger sites may seek to improve their crawl efficiency to ensure that the ‘right’ pages are being crawled more often. The use of robots.txt, internal link structures and specifically telling search engines not to crawl pages with certain URL parameters can all improve crawl efficiency.