Cost-per-click (CPC) bidding means that you pay for each click on your ads. For CPC bidding campaigns, you set a maximum cost-per-click bid - or simply "max. CPC" - that is the highest amount that you are willing to pay for a click on your ad (unless you're setting bid adjustments, or using Enhanced CPC).
Your max. CPC is the most you will typically be charged for a click, but you will often be charged less -- sometimes much less. That final amount you are charged for a click is called your actual CPC. The actual CPC is calculated using this formula:
Actual CPC = AdRank of the ad below yours divided by your Quality Score (+ $0,01).
If you enter a max. CPC bid and someone clicks your ad, that click won't cost you more than the maximum CPC bid amount that you set. You'll choose between manual bidding (you choose your bid amounts) and automatic bidding (let Google set bids to try to get the most clicks within your budget). CPC pricing is sometimes known as pay-per-click (PPC).