Once your campaigns have been set up, there are many different pieces of data that you can analyze in AdWords. AdWords allows rich customization of your campaign management page, so that you are looking at data that is most pertinent to your analysis. The default view will most likely not include all of the information that you'll need as you review performance and optimize, and you'll need to customize the views to include the metrics of interest.
Think about what data is useful for a particular analysis. For example, you may wish to review performance data at the campaign level so that you can decide which campaigns are generating the most clicks and conversions.