One of the on-page optimisation process. Actually,anchor text is the visible text of hyperlink.
Behind this text,there is a hyperlink that makes you to enter in to the website page.
It must be perfect,because search engines crawl mainly depends on these hyperlinks.
It must be coincide with the content given in the web page.
The search engine spiders are not only looking for text, but also are interested in the keywords you utilize in your anchor text for links.