Get Google's view of your website, and diagnose potential problems.
See how Google crawls and indexes your site and learn about specific problems they're having accessing it.
See how your site is performing.
Learn which queries drive traffic to your site, and see exactly how users arrive there.
Share info with Google to help them crawl your site better.
Tell them about your pages: which ones are most important to you and how often they change. You can also let them know how you would like the URLs they index to appear.