Banner ads are advertising on a web site that promotes and links to another site. Banner ads are ubiquitous on the Internet as a powerful method for a site to leverage its traffic to benefit another.
referral link compensation
Many forms of compensation for adding referral links on a site. Below is a list of the more popular ones.
Pay per impression
A site receives payment for each time they display a link
Payment for click through or commissions on purchases
Both sites get a link to one another