Google Webmaster Tool
The information displayed in the graph charts, by keyword hits, visitor demographics, locations, links to your site and so on. These information are useful to help you improve your website, especially in content development. You will aware of what kind of content is popular or having great tendency of drawing crowds.
Of course, some simple steps needed to taken up to set up the google webmaster, as well as porting your website it, so that you can analyze your site using google webmaster tools.
It eventually become your income if you manage your websites/blogs well. The traffic of visitors are the source of income. As you getting generating more traffic from your website, you may subscribe to some web advertisement program that help you to generate income. Such as Google Adsense, Nuffnang, AdHitz, adf.ly etc.
Basically, these programs serves advertisements to your site. As the users clicked on the ads, you will able to receive some commision for the company of the program respectively.
Besides, this can be depends on how much of the advertisement being served too. Once you hit the target number of advertisement served (usually they call this impression), you will received comissions.