This document provides an introduction to search engine optimization (SEO) by discussing search engine basics, popular search engines and their market shares, and why optimizing a website is important. It explains how search engines work by crawling websites, indexing documents, processing queries, and ranking results. The document also outlines ways to optimize a website through metadata, keywords, links, social media, and following best practices instead of black hat techniques. The goal of SEO is to improve a website's visibility in organic search results.