An action taken after viewing an online ad, usually leading to a view of the advertisers web site, or some other desired landing page.

In advertising a "click" is used to mean a request for a page that contains an ad. Sometimes, a click is more narrowly defined as "a click on an ad". The click rate is the number of clicks (on an ad) as a percentage of the number of times that the ad was downloaded with a page: a click rate of 2% means that 2% of the people who downloaded the page clicked on the ad.

an action, and a positive action should results in a higher level of final actions, ultimately in sales of something

Action of clicking with a pointing device to change current setting of a page.

Through - The action of clicking on a link to visit a web page.