Which of the following terms can be used to describe the amount of times a unique user will see an ad over a certain time period?

Frequency refers to the average number of times a unique user sees an ad over a given period. It helps advertisers understand ad exposure and prevent ad fatigue. Reach, on the other hand, is the total number of unique users who saw an ad, regardless of how many times they saw it. Engagement rate measures how users interact with an ad (e.g., clicks, likes), not how many times they see it. An impression is a single instance of an ad being displayed, but it doesn't account for unique users or repeated views by the same user.