This document provides an overview of search engines and search engine optimization (SEO). It defines search engines as internet tools that search an index of documents for specified terms and return relevant results. Popular search engines like Google, Yahoo, and MSN are described. The document outlines why SEO is important for driving qualified traffic to websites and increasing sales. It then explains basic SEO strategies like keyword research, on-page optimization of titles, headings and content, and obtaining high-quality backlinks. Ranking factors that search engines consider like on-page elements and link popularity are also summarized.