Ad revenue refers to the income generated by displaying advertisements on a website, television channel or other medium. It is typically calculated based on the number of impressions (views) an ad receives and the amount of money that the advertiser has agreed to pay for each impression. Advertisers are willing to pay because they believe that their message will reach potential customers through these platforms. The revenue generated from ads can be a significant source of income for websites, media companies or content creators who use them to monetize their platform and support their business operations.