From "Traffic Planning", you can search the specific apps/sites and sellers by selecting the options on the left column.
The Platform-Wide Data shows an overview of the traffic. The Placement-Specific Data shows traffic from each app/site and seller.
Click on an app/site, you will see the detailed information of this app/site.
Maps are shown on different levels of color. The deeper the color is, the more impressions it offers in that country.