It is Cost per click.
Just like CPM , CPC is also a measurement used in online advertising , the only difference is this cost is based on clicks and not impressions . If any user is shown the Ad but he doesn’t clicks on it their won’t be any cost effect as the cost is based on clicks only.
Example : If CPC is $5 , it means every click costs $5 so 20 clicks than it will cost us $100.
*Also , consider a campaign where payment is based on impressions, not clicks. Impressions are sold for $10 CPM with a click-through rate (CTR) of 2%.
1000 impressions x 2% CTR = 20 click-throughs
$10 CPM / 20 click-throughs = $.50 per click.