concrete5's default style of URLs includes index.php. This is an essential part of how concrete5 handles requests for pages. For example, the path to a page named "Example" located directly underneath "Home" on your sitemap would render at a path like so:
As as site owner, though, you'll likely want your URLs to display in a more elegant manner. Pretty URLs provides an easy way to remove the reference to index.php to users and search engines alike while letting concrete5 continue to work as usual. With Pretty URLs enabled, your page's path will now look like this:
When you enable Pretty URLs though System & Settings, concrete5 will attempt to add code to a hidden file (located at the root of your site) named .htaccess. The code concrete5 generates and tries to add to .htaccess is shown above. It may differ slightly depending on your server's configuration and the location of your site.
Tip: If you're having trouble with Pretty URLs, it's a good idea to check out what code exists in your .htaccess file and see what's going on.