What is anchor text?
Anchor text is the text used to display as a link. For example, in
Adsense Tips
'Adsense Tips' is the anchor text of this link.
Anchor text is considered one of the most important factors behind SERPs. Search engines pretty much recognize the theme of a site by analyzing the anchor texts of off-site links from other sites. It's like an opinion posed by the linking site about what the linked one is about.
Anchor text optimization is the main topic of off-page SEO.