Having an SEO-friendly URL structure can help search engines and users alike navigate your website more easily, potentially giving you an edge over the competition.
To explain the basics, contributors John Lincoln and Brian Dean have put together this helpful infographic.
Have a look at Search Engine Land for the full article.
http://feeds.searchengineland.com/~r/searchengineland/~3/_ofvLpH3HL0/infographic-ultimate-guide-seo-friendly-urls-249397