What are they?
Search engines help us find content on the web. They have a vast database that is continuously updated. Depending on the key words, they return results that are relevant. Different search engines do this in different ways and rank the pages differently.
Search engines have bots called "spiders" or "web crawlers" that are continuously scanning the Internet for content.
This is the process of storing and organizing the websites and content that is crawled.
This is where the engines rank the pages on the basis of certain criteria; different algorithms for different search engines. But all of them penalize spammy content, slow loading websites, bounce rate, suspicious activity or content, and so on.