CPC (cost per click) means „cost per click“.
It describes how much money an advertiser has to pay when someone clicks on their online ad. So you only pay when someone actually clicks - not when the ad is only displayed.
Example:
If an ad costs a total of CHF 100 and receives 50 clicks, the CPC is CHF 2 per click.
Interested in other topics? Here we have a few more suitable explanations.