How earnings are generated from clicks and impressions
The way you generate earnings will depend on the type of ads which have been displayed on your site. You can receive earnings for valid clicks on cost-per-click (CPC) ads and valid impressions on cost-per-thousand-impression (CPM) ads. Please keep in mind that CPC ads will appear by default, and CPM ads will only appear if an advertiser has bid to run ads on your site through placement targeting. At this time, it's not possible to request CPM ads for your site or set your account to be paid only on a per impression basis.