A launcher for Android handles the way you interact with your phone. It decides where you can put your app icons, and how the touch menus interact with the user. Basically, it's what decides that your App Drawer button should look like a group of dots, or that your browser icon should be a round globe.
If you've had an Android phone for a long time you might want to try different launcher applications to switch things up. Alternatively, if you're converting from a Windows Phone 7, one app can make the transition quite a bit easier. … Read more