Just about every Mac ever built is network-ready. Buy a few cables and adapters, and you can connect all the computers in your office together, with or with-out wires. The process of rigging the hardware and software for a network is somewhat more technical than, say, emptying the Trash, but it's not exactly rocket science.
Once you've got a network, you can copy files from one machine to another just as you'd drag files between folders on your own Mac. You can send little messages to each other's screens. Everyone on the network can consult the same database or calendar. You can play games over the network. You can share a single printer, cable modem, or fax modem among all the Macs in the office. You can connect to this network from wherever you are in the world, using the Internet as the world's longest extension cord back to your office. And in Mac OS X, you can even connect to Windows machines.
Best of all, all the software you need to create such a network is built right into Mac OS X.
As you read this chapter, remember the difficulty Apple faces: It must design a networking system simple enough for the laptop owner who just wants to copy things to a desktop Mac when returning from a trip, yet secure and flexible enough for the network designer at a large corporation. In general, you'll probably find that Apple has done an excellent job of balancing these two wildly different motivations.
You don't necessarily need a network to exchange files between ...