The home tab shows an overview of how your account is performing and has the following sub-components to it:
Campaign Tab acts like a platform from where you can manage all your campaigns. This is the tab where you will probably spend most of your time within AdWords.
Campaigns tab has three main areas: campaign tree, navigation tabs, and stats area as shown in the following screen shot.
The opportunity tab offers suggestions and tools to help you improve your account. For example, keyword suggestions, bidding suggestions, and ads diagnostic tools are just a few examples of different options available in this tab.
All information related to billing can be found in the Billing tab by clicking on the Billing Summary tab. This is where you will come to see your current account balance and the history of your payments.
Also, if you need to change your billing information, such as credit card number, or you want to add a backup payment method, then you will use the Billing Preferences option available in this tab.
This tab allows you to manage administration of your account including changing account preferences, editing notification settings, and granting access to other users.