Inbound Links:
the number of pages linking to your Web page affects your PageRank score. However, there are also other factors regarding inbound links that are distinct from the PageRank score that affect the term vectoring score. Google also considers the anchor text of a link in determining the page's term vector score. When Google considers the text of the page it not only considers what the author wrote and actually put on the Web page, it also considers what other people wrote when they linked to that Web page.  It does not matter if the site linking to you is not related, however, as stated, the text that describes the link to your site is of importance.