Average cost-per-click (CPC) is the amount paid for your ads divided by your total clicks.
What it isn't: Average CPC isn't the same thing as maximum CPC – that's the most that you're willing to pay for a click on your ad. You won't be charged more for a single click than the maximum CPC that you set.
Example: If your ad receives two clicks, one costing £0.20 and one costing £0.40, your average CPC for those clicks is £0.30.