This document discusses search engines and search engine optimization (SEO). It begins by defining what a search engine is and explaining what SEO is and is not. It then covers differences between major search engines, how search engines work, standard web search engine architecture, SEO software components like crawling and indexing, and traffic sources for websites like organic search and referral links. The document also provides tips on keyword research, content optimization, and how links can help rankings. It explains how to perform search queries and techniques to avoid. In under 3 sentences, the document provides an overview of search engines and SEO strategies and techniques.