switch

1. A network switch is a computer networking device that connects network segments.

The term commonly refers to a Network bridge that processes and routes data at the Data link layer (layer 2) of the OSI model. Switches that additionally process data at the Network layer (layer 3 and above) are often referred to as Layer 3 switches or Multilayer switches.

The term network switch does not generally encompass unintelligent or passive network devices such as hubs and repeaters.

2. Electro-mechanical device having distinct states, usually ON and Off, (or open and closed).

Part 1 taken from:
http://en.wikipedia.org/wiki/Network_switch