What are DMAs?
DMA stands for "Designated Market Area" and is a region that can be offered the same media. In the Cliques context, it's the most specific region you can target your campaign to.
By definition, DMAs are "the geographic areas in the United States in which local television viewing is measured." For marketers and advertisers, they are the key to targeting specific geographic areas.
As you can see in the map below, some DMAs cover much larger expanses than others. Let's say you're looking to enter the urban running scene in New England. You can begin by targeting only the Boston DMA, or by giving more weight to available impressions in that region through the Cliques Console. This allows you to track if your campaign is successful in that market (i.e. if you have a high ROI). If it is, you might want to increase efforts in that region. If it isn't, you might change your focus to another area, like the San Francisco DMA.
You can find the full list of DMAs as published by Nielsen by clicking here.