This is a pretty good explanation: " Friendly URLs that are short and easy to remember are considered "user-friendly URLs." These URLs help visitors remember web addresses, which means they can revisit pages by simply typing in the URL address bar. For example, a company may use the URL "www.[company].com/support/" for the support section of their website. This is much easier to remember than a long convoluted URL, like "www.[company].com/section/support/default.aspx?id=1&lang=en". "