From IAB Wiki
A click can denote several different things.
- It can be a metric that measures the reaction of a user to an Internet ad. In this context, there are 3 types of click:
- in-unit clicks
- It can be the opportunity for a user to download another file by clicking on an advertisement, as recorded by the server.
- It can be the result of a measurable interaction with an advertisement or key word that links to the advertiser's intended Web site or another page or frame within the Web site.
- It can be a metric that measures the reaction of a user to linked editorial content.