Google analytics generates statistics. Who visited your site, when, from where, how often, wich browser,...?
First you need a google account. If you have a Gmail address you already have one.
Now you need a tracking ID, connected with your site.
It looks like this. Your account is connected with one or more sites.
The tracking - ID looks like this. Look at the code. You don't need this code when you use the Drupal module!
Configure the module..
The code is visible in the source. The statistics will start now..