Add new ad units

Ad units represent the spaces on your website or app where you want to show ads. An ad unit defines such attributes as the size of the ad format that can show in the ad space. 

1. When you create an ad unit, Ad Manager generates a tag (a snippet of code) for each ad unit.
2. This tag is then inserted into your webpage or app.
3. When a user visits the webpage or app, the ad tag makes a request for an ad from Ad Manager. 
4. Campaigns that reference or "target" the ad unit are then eligible to serve an ad to that request.