Google webmaster tools is handy in too many ways to go into here. I would have advice you to go have a look and read online what you can do with it.
You will need a gmail account to actually work with it, but that is easy to create.
I mainly use it to get the verification code, place the verification code in the meta tags and then verify the site. You can also add your sitemap there and if there is a mistake in the sitemap google master tools will help you correct it.
Another good tool from Google is the link below, specially when you are trying to find the right keywords for you meta tags. You do not need to sign up to adwords to work with this. Just do not click on the add on the left. You can test various keywords and combinations of keywords for seach volume etc. A lot of Seo people use this tool.