It refers to an act of clicking on advertisements online that is targeted towards the advertiser.

One way of measuring your success in an advertising campaign online is to measure the rate of click-throughs. This in turn is calculated by dividing the total number of users who clicked on the ads with the number of impressions. A direct and accurate approach to count the click-throughs would be to exclude duplicate clicks and robot clicks. This approach attracts lots of importance as it will be made use of to measure the click-throughs; based on which the payments are determined. Over a period of time, the CTRs or Click-through rates have seen a downfall considerably. This is particularly so for banner ads that is averaging around 1 per cent.