When you first connect your iOS device you need to register it. In this video you will see how this is done on an iPod. Once your computer and device are paired you can download content (apps, music, podcasts and more) through the device or though the computer. Synchronizing pairs the content.
Just getting started with a iOS device – in this case an iPad. At some point in the process you need to create an Apple ID. This video shows how you can register for an ID in the process of downloading an App.