You can buy FB ads either on a CPM or a CPC basis.
If you buy CPC ads, FB shows your ads to users who are more likely to click on ads, but you'll pay a lot for this service.
CPM prices are much cheaper. From my experience if you've got a CTR of over 0.025% (1 in 4000 views) then paying CPM is cheaper than CPC. And you should be able to get a CTR over that for most things.
General opinion among the FB ads community seems to be that paying CPC is a suckers games, FB are just using CPC pricing to exploit unsophisticated ad buyers.
If you buy CPC ads, FB shows your ads to users who are more likely to click on ads, but you'll pay a lot for this service.
CPM prices are much cheaper. From my experience if you've got a CTR of over 0.025% (1 in 4000 views) then paying CPM is cheaper than CPC. And you should be able to get a CTR over that for most things.
General opinion among the FB ads community seems to be that paying CPC is a suckers games, FB are just using CPC pricing to exploit unsophisticated ad buyers.