Crawling is the process by which search engines discover updated content on the web, such as new sites or pages, changes to existing sites, and dead links. To do this, a search engine uses a program that can be referred to as a ‘crawler’, ‘bot’ or ‘spider’ (each search engine has its own type) which follows an algorithmic process to determine which sites to crawl and how often. As a search engine’s crawler moves through your site it will also detect and record any links it finds on these pages and add them to a list that will be crawled later. This is how new content is discovered.
I used to wonder what it had to do with the web.
I like how you have broken down those elements!