At least, on a Mac or other Bonjour-enabled device, they are. With Bonjour, the computer can find a Bonjour-equipped printer on the network. The user does not need to know where on the network the printer's server is located.

The way I understand it, the technology works like this: When the printer connects to the network, it's Bonjour server tells your network's DNS server that it is active. It also tells the DNS server what it can do for other devices (in this case, handle print jobs, and maybe even fax jobs and scan jobs), as well as what ports other devices should use to "talk" to the server, as well as other relevant information. Then, a Bonjour-compatible device looking for a printer will query that DNS server. The DNS server will respond with the information given to it by any Bonjour-compatible printer on the network.

Edit: BTW, Windows users can download Bonjour. I think it's available as a stand-alone program and packaged with iTunes.