Frequency capping
By frequency capping, the campaign attempts to limit the number of times your ads are shown within a certain time period. The goal is to avoid over-exposure of the same ad many times to the same user. This technology is browser and cookie based, it works well on mobile and personal desktop devices.
Frequency tracking works less well on shared devices such as Web TV, streaming services and on devices where users have turned off their cookies or limited their ad options.
Frequency capping often works well on personal devices like desktop and mobile. But your ads might not be shown on shared devices, streaming services, WebTV etc.