Old Guestbook
Guestbooks in the Site Builder can be used for many different things- any time you want to get limited feedback from people who visit your site. Every time a message is left, you will get a notification via e-mail. You have the option to respond to a message, removed messages, or even edit messages.
The first thing you will need help on is Starting a Guestbook
After you start it, you'll need to move on to Administering a Guestbook