Short for remote wake-up, a generic term for the action of turning on a computer over a network from a remote location. Often, IT personnel prefer to maintain client systems after employees have gone home. Even if these tasks are automated, client machines must be left on. In the past, if they weren't left on, personnel had to manually turn them on. But, with wake-on-LAN, client systems can be remotely and automatically powered up.
Wake-on-LAN is considered a form of remote wakeup, but not all RWU systems are Wake-on-LAN as it is possible to wake a computer remotely using a dial-up connection from outside a local-area network.