A favicon (short for favorite icon), also known as a shortcut icon, website icon, tab icon, URL icon, or bookmark icon, is a file containing one or more small icons associated with a particular website or web page. A web designer can create a favicon in several different ways. They then upload the favicon to a website (or web page), and the web browsers will make use of it. 

Browsers that provide favicon support typically display a page's favicon in the browser's address bar (sometimes in the history as well) and next to the page's name in a list of bookmarks. Browsers that support a tabbed document interface typically show a page's favicon next to the page's title on the tab, and site-specific browsers use the favicon as a desktop icon.

In Storefront 2.0, the favicon is saved in the root directory. 

Learn more about favicons here.