Google uses the link anchor text contained in links pointing to your web pages to help rank your pages for search terms.For example, if you have a bunch of backlinks (links on other sites pointing to your web page) with a couple of your keywords in the link anchor text, your page will likely be ranked pretty well in Google when someone does a search on those keywords.Using your keywords in the link anchor text of as many inbound links to your web pages as possible is one of the most effective SEO strategies that you can use. Of course, "keyword rich" link anchor text is even more effective when used in combination with other SEO techniques as well.
Thanks