A contextual link is one in which the clickable text is made up of a keyword phrase you want to obtain a page one listing for in Google.

For example, I'm personally interested in the phrase lead generation. I attempt to secure as many contextual links back to my main site's homepage as I can.

A contextual link can only work if it links to a page primarily about the keyword phrase. For example, the phrase perspex furniture should link to a page about furniture made from...