Ad reach rate. In the case of Internet advertisement, the ratio of the number of advertisements delivered to all Internet users. Especially the indicator used to measure the effect of banner advertisement. Frequency is easy to be confused with, but ""Frequency"" is an index to measure ""number of times"" how many times an advertisement was exposed to one person. ""Reach"" is the ""percentage"" of those who saw the advertisement. ""Reach"" may simply refer to the number of people to whom advertisements were delivered. In this case, ""reach"" has the same meaning as ""number of unique users"". When considering the effect of banner advertisement, indicators such as ""reach"" (how many people can see the advertisement) and ""frequency"" (= how many times you can see the advertisement) are important. Whether to emphasize ""reach"" or ""frequency"" depends on the content of the advertisement. For example, suppose you have a banner advertisement A with a reach of 25% and a frequency of 2, and a banner advertisement B with a reach of 7% and a frequency of 5. Which advertisement is effective? If the content of the notice is impactful so that you can recognize the content as soon as you see the advertisement, you should choose banner advertisement A with more emphasis on reach rather than frequency.