What is frequency capping in AdWords?

CPM : Cost Per Thousand is the amount you pay per thousand impressions that you receive, regardless of the number of clicks you receive.

CPC : Cost Per Click is the amount you pay for each click.

CPV: is when advertisers pay for each unique user view of an advertisement or website.

It is used more on video marketing such as YouTube campaigns.

Frequency capping is putting a limit on the number of times an ad is shown to an individual. In Google AdWords, you can enter a maximum 'cap' on how many times someone can potentially see a display campaign. You can set these caps at the campaign, ad group, and ad level and further segment them by day, week, or month.