If your office has more than one computer, you’ll want to share information between them.
Some people just send emails back and forth to keep them up to date. That does work, to a point.
If those two computers are both connected to the internet, you do actually, already have a network, you’re just not using the network’s potential.
One major advantage to sharing documents from a single source, either on a server or simply on another computer, is that everyone accessing that document knows they are all looking at the same version.