An ad tag is an html tag that is placed in your source code in the location where you want ads to appear.
An ad tag can be linked with an ad zone. If an ad tag is not linked with an ad zone, ads not targeting any zone will appear there. If an ad tag is liked with an ad zone, only ads targeting that zone will appear in the location of the ad tag.
<div class="adplugg-tag" data-adplugg-zone="topbar"></div>