Well, the Netlink is a great modem for Saturn that lets you play games online. You can also surf on the internet with and and send email. There are some really great games released for netlink for example Virtual On, Duke Nukem 3D, Sega Rally and Daytona USA CCE.
I'm not sure exactly how it works, as I don't have one, but I know that if you want to play a game against someone one of you has to dial to the other person. That's one of the reasons I haven't gotten one, as there wouldn't be anyone in my area that has it, and I wouldn't have the extra money to pay for the long distance calls.