Re: How am I billed for Instream ads?
Cost-per-click (CPC) bidding means that you pay for each click on your ads. You set CPC bids to tell Google how much you're willing to pay for each click.For more information Go with this Link.
Cost-per-impression(CPM)you bid for your ad based on how often it appears on the Google Display Network. You set the max amount you want to pay for ads, whether they're clicked or not. For more information Go with this link
Hope it helps you.