Anchor texts are those small texts you get to see in between the embed code when you are linking to a website. There are many strategies and practices used for making sure your website maintains a good ranking in search engines. Search engines analyse text and look for keywords and links in order to rank your page accordingly.
Although the keywords have been affected by Google's Penguin update in 2012. Google stopped looking for keywords which were too common and so instead, many websites started using anchor texts for search engine optimizations. You can use online tools such as negative keyword tools to look up for words that won't be helpful if you use them in your web content.