Frequency capping is a feature that limits the number of times that your ads appear to the same person on the Display Network.
Frequency is the average number of times that a unique user sees your ad in a position of '1' over a given time period (day, week, or month).
It's important to use frequency capping to prevent annoying your potential customers, especially in remarketing to them.
When you turn on frequency capping for a campaign, you set a limit for the number of impressions that you'll allow an individual user to have per day, per week or per month. You also choose whether the limit applies to each ad, ad group or campaign.
Only impressions that were viewable count towards frequency caps. An ad is counted as viewable when 50% or more of the ad is shown for one second or longer for display ads, and two seconds or longer for video ads.
Frequency capping is not available as an option for the Search campaign but is an option for the Display campaign and Youtube campaign.
To access the frequency capping menu, go to google ads > campaign > settings > additional settings > frequency capping.