My Mac, the Server?

I admit I don't know Macs, I don't know networking, but is it normal that when I connect to the internet via my Airport Extreme my entire home folder becomes a server? Am I just not "getting" the way my Mac operates? When I connect to the Internet, the Server icon shows the following: Does that mean I am sharing my home folder (all users, all info) or that it is public? If my computer is a server, who is the client? I honestly hope I am being ignorant and paranoid here, but something seems amiss.