It is hardly difficult to guess from the name itself that Google Webmaster Tools is a set of tools for webmasters. However, what you don't know right away is that this is a very useful toolset that allows you to communicate with Google and adjust many aspects of how Google sees your site, such as list the external and internal links to your site, adjust the crawl rate at which Google bot indexes your site, check the keywords users typed to land on your site, as well as the click through rate for each keyword, see your site's statistics, and many more.