Google Webmaster Tools also allows to know if your site is infected with malware. ... Google Webmaster Tools is a really valuable instrument for SEO. It gives you at a glance data about all important SEO aspects of a site, such as keywords, links, crawl errors, etc.

Google Web Master is a place where Google communicate the problems with your website. This tool is used to crawl errors. Suppose, you are facing the problem of parameters or you want to see how many pages are in index and much more. It is basically for site performance tool that depicts the performance of the site.