The favicon is pretty much normality these day. the interesting bit here is the apple-touch-icon which is used if you save a bookmark to your home screen on an apple touch device such as an iPad or iPhone. Interestingly enough, android also supports its usage. As far as I can tell, the apple-touch-icon size is 60px by 60px. As the comment says, if your icons are in the root of your domain, these links aren’t required.