A link wheel is a technique that can be very effective in raising a site’s popularity with Google. In short, a link wheel is a number of sites that each holds an article that links to one common site (your site). The phrase "link wheel" refers to the situation when these sites not only link to one common site, but also link to other sites in the "wheel." The effect is that each site that links to your site also receives links from other sites, making Google feel as if each site is more "authoritative" or important. Below are a number of figures that illustrate how a link wheel is developed.
A link wheel begins with one site that includes an article that links to your site. It’s common to have this article-holding site be a "social media" site such as a WordPress, Blogger, or Weebly site:
The above is repeated with a second site, again with an article that includes a backlink to your site:
Here's where the "wheel" effect starts to take place. The article on the first site contains a link to your site, and additionally it includes a link to the second site:
This process is repeated multiple times:
In the above figure the purple arrows are what brings about the "wheel" effect.