In Joomla 3, once you enable Search Engine Friendly URLs (obviously for better Search Engine Optimization), you will probably get index.php in your address.
Something like www.yourdomain.com/index.php/about-us.
If you want to remove the index.php, it is very simple. Besides enabling the Search Engine Friendly URLs, you’ll also need to enable URL rewriting.
Quick Steps:
1. Go to Global Configuration
2. Enable Search Engine Friendly URLs
3. Enable URL rewriting
Note: If you want more SEO benefits it would be a good idea to install Joomla components for SEO
