Anchor Text Optimization
From Link Building Wiki
Anchor Text Optimization refers to the technique of including specific keywords as the links pointing to your website or internal pages in order to help Google's ranking algorithms understand what your site is about. By having valuable content on your website and pages, search engines attribute credit that can increase web rankings as well as PageRank.
For instance. If I am trying to optimize my web hosting site to rank well in the Google Serps for the term "web hosting", I would want to link to my site by using the words "web hosting" in the Anchor Text of my Inbound Links. This is a very basic definition.
The subject of Anchor Text Optimzation can get very technical. When webmasters and SEO's first starting learning about how powerful it was to optimize the anchor text of their Inbound Links, they were quick to find ways to take advantage; because of that, Google was forced to find ways to minimize the power of Anchor Text Optimization.
Over the years Anchor Text Optimization has become much much more coplex, but still remains a critical component to any link building program.