What is favicon
A favicon is a small, 16x16 image that is shown inside the browser's location bar and bookmark menu when your site is called up. It is a good way to brand your site and increase it's prominence in your visitor's bookmark menu.
How to change favicon icon
To change favicon icon, just replace the favicon.ico icon from the theme folder (pari) with your own favicon icon. Name of favicon icon must be favicon.ico
There are many websites like Dynamic Drive FavIcon Generator which allows you to create your own branded favicon icon. Please use Google.com to find more similar websites for creating and generating favicon icons.