Facebook works on a bid on a cost per click or a cost per thousand impressions. Each time a user views a page that displays ads or Sponsored Stories, an auction takes place to determine which eligible advertisement will be shown on Facebook.
Bidding is the amount on each ad you are willing to spend per click or per thousand impressions. It all depends how much your competition is willing to pay for that same advertising space on Facebook. That will however determine where your advertisement will be and how many times it will be displayed on Facebook.
For Example; if you bid R1 CPC for your ad, you're indicating that you are willing to spend up to R1 for a click on that ad. However, if our system determines that your ad can win the auction with a bid of only R0.60, you'll only be charged R0.60 for that click.
If an ad doesn't perform well when it's first running on our site, or if its performance declines over time, our system will determine that this ad is less likely to perform well in the future and will display the ad less often.