What is an Impression?
An impression is a metric used to measure an ad's appearance on a web page. Impressions are often called an "ad view". They are used in online ads, which also costs on a per-print basis. In search engine marketing, counting impressions is central to how web advertising is accounted for and paid for. Impressions are not a measure of how an ad was clicked on but only that it was shown, which leads to some controversy about how precise the metric is.
Breaking Down Impressions
Broadly speaking, one impression is equal to each event of locating and loading a web page. Since it is both observable and understandable, it has become the most efficient and inexpensive way to assess whether or not an advertisement is being used. But the precise meaning of that figure is up for debate.
Some online advertising experts think there is no perfect way to count impressions because, for example, a count can be distorted by a single person reporting the same ad in several page views. There are even other ways to distort overall impression figures, which causes marketers to look with a bit of suspicion at any impression figure.
In general, most advertisers and publishers determine beforehand whether to measure and account for the impressions. Advertisers can determine whether or not a campaign is successful based on another type of coverage, such as interaction (broadly, how a viewer interacts with an ad).
Accounting for Impressions
Impressions are also calculated by cost per mile (CPM), where mile corresponds to 1,000 impressions (or cost per thousand impressions). A banner ad may have a CPM of 4$5, which ensures that the website owner earns $5 for every 1,000 shows of the ad on his website.
Increasing ad impression may be charged to the owner of a website. Many advertisement deals can only be charged by the website owner when a user clicks on the ad, or only when the user clicks on the ad and makes a purchase.
Usually, advertisers pay less for an impression-only ad campaign, and more for click-throughs and conversions-based initiatives. The explanation for this disparity in pay levels is that an ad that encourages the audience to take action resulting in a sale is more beneficial for the advertiser as compared to the one that does not.
