A network drive is a disk that is accessed using the network. For example, file sharing involves mounting a network drive.
A network drive behaves very similarly to a local disk.
Macintoshes running OS X 10.4 will remain awake as long as another computer is connected to it. Because of this, it is a good idea to eject network drives when you're done with them.
If you are running OS X 10.0 through 10.3 and your network drive's computer goes to sleep or shuts down, Finder will hang for a few minutes while the connection times out.