Link wheel, as the name it speeks, is the wheel of the links.
In which you need to create unique content for some web 2.0 website and link them in form of cycle.
For instance,
If you have post 5 content on 5 different web 2.0 websites names as, A, B, C ,D and E
Then content in website A should link to content in website B,
Then content in website B should link to content in website C,
Then content in website C should link to content in website D,
Then content in website D should link to content in website E,
Then content in website E should link back to to content in website A
this will form a link to your content and so known as link wheel.