Ad unit
A set of ads displayed as a result of one piece of the AdMob ad code. You can create and customize an ad unit in your AdMob account. You can name your ad units and manage their settings in your account.
Ad units are containers you place in your apps to show ads to users. Ad units send ad requests to AdMob, then display the ads they receive to fill the request. When you create an ad unit, you assign it an ad format and ad.
Learn more about ad units, ad formats, & ad types.