An Ethernet splitter physically splits an Ethernet connection into two connections, and only one connection can be used at a time. An Ethernet switch splits an Ethernet signal into multiple signals, each of which can be used simultaneously.
An Ethernet splitter requires no power input, since the splitter is simply taking a single Ethernet connection and physically spitting it into two Ethernet connections. When a device is hooked up to one of the connections, the Ethernet signal is fed entirely to that connection, and the other connection receives no Ethernet signal. Therefore, only one device can be powered on and operating at a time. If two devices are connected and powered on simultaneously, the splitter does not work, and neither device receives an Ethernet signal.
An Ethernet switch can be used for networks containing unrelated devices, such as a computer and a video game console. On the other hand, an Ethernet switch requires a power input, since the switch takes an Ethernet signal and divides it into multiple signals operating simultaneously. Since these signals operate simultaneously, multiple devices can be connected to the switch and operate simultaneously. An Ethernet switch is ideal for networks requiring multiple computers to be connected, since each computer requires an Ethernet connection.