Sharing web address is a common thing in internet. you may share address of a download link, favorite video clips, or may be some stuff for education. Some of these address should be very large right?
But you know, these address can be shorten using some web services and if anyone visits this link, you will be get paid. Excited? they are not mad to give you free money. Whenever you shorten a web address, they will also put some advertisements in that page. They are actually paying for these ads.