Aggregate Data allows you to view reports based on information from all of your AdSense channels. If you don't have any channels set up use this option. In the long run, to measure the effectiveness and efficiency of your AdSense setup, it is best to create different channels for each segmentable set of ads. Once you've done this, then you can create reports based on the data from the individual channels. Channels can be a very powerful tool to help you optimize your approach to AdSense. Good luck!