To classify your inventory better you can use the following optional global Picklist Value Sets for Site, Placement, and Ad type. Starting with version 2.92 you will also find these value on your campaign items to help control 7.2.14 Publisher Payouts (BETA) and 4.16 How to handle Commitments (Financial Agreements) better. 

Site

Placement

AdType

More Information

Learn how to edit the Global pick-lists here 7.2.1.2 Edit Picklist Values Sets (Global Picklists). Use this classification in 4.16 How to handle Commitments (Financial Agreements).