SEO best practices dictate that you include relevant keywords in a number of prominent areas on your site, from the titles and body text of your pages to your URLs to your meta tags to your image file names. However, successfully optimized websites tend to have thousands or even millions of keywords. You can't very well craft a single, unique page for every one of your keywords; at the same time, you can't try to cram everything onto a handful of pages and expect to rank for every individual keyword. It just doesn't work that way!