Most of the time when people talk about affiliate marketing they are describing a system where site A advertises products from Site B and gets paid each time someone makes a purchase after clicking a link on Site A. However this article is describing a slightly different scheme – basically link exchanges. Site A will link to Site B and Site B will link to site A. It may be because the two sites are friends, own related websites or simply want to recognise each other. Either way it’s an easy way to get some free promotion for both websites – a free linkback and plenty of hits.