Searching for Searches

Today we have Search Engines on the table, and I am mostly spitballing to help myself better understand how they work. When you search a keyword, the search engine pulls up relevant links based on past data about what people have clicked when making this search before. Web Crawlers analyze and coagulate all this data. The search engine determines which link are relevant based on content, accuracy and date of creation. Stemming allows search engines to widen their search parameters to match different verb tenses and pluralities of a keyword. Directories, which Yahoo used when it was made sort websites into categories to provide related searches, which are generally less effective than search engines. I feel like I've got all this down.