Let's start by getting a clear definition of what it means for a site to have Search Engine Friendly URLs.
Sites created with content management systems like Joomla! rely on interaction with the database for the display of content. Accordingly, the URLs often include query strings and other characters that are part of the interaction with the database. A simple HTML site doesn't have this issue; instead, its URLs are typically much simpler and lack the complexity seen in a CMS-powered website.
URLs containing query strings and other odd characters are hard for both humans and search engines to read. Ideal URLs are readable and tell us something about the content of the page. By default, the Joomla! system produces complex URLs containing additional characters that serve no useful purpose for the site visitor. Accordingly, your first step towards making Joomla! more search engine friendly is to get rid of the messy URLs and replace them with Search Engine...