Stands for "Click-Through Rate," and is used in online advertising. Web publishers typically generate revenue from advertisers each time a visitor clicks on one of the advertisements (the PPC model). Therefore, publishers are interested what percentage of page views result in clicks on the advertisements. The higher the click-through rate, the more revenue a publisher will generate. So, what would you guess is a common CTR for a website? 10%? 5%? Try 1%. Since the average CTR across the web is only around 1%, publishers need to attract thousands of visitors each day to generate substantial revenue.