There are several locations that facebook can server your ads. These the types and their definitions.
desktop_feed - News Feed on Desktop Computers
mobile_feed - News Feed on Mobile Devices,
sponsored_result - Sponsored Search Results
mobile_external_only - External Ads on Mobile Devices
non_feed - Right Column Ads on Desktop Computers
right_hand - Right Column Ads on Home Page for Desktop Computers
logout - Logged Out Home Page
unknown - Unknown Placement
In ReportGarden, you will find these types in the data from Facebook.
If you have any other questions, please feel free to email us at [email protected]