Switch

In Networking terms a switch is a device that filters and forwards packets of data between LAN (Local Area Network) Segments. Switches operate at the data link layer which is second on the on the OSI list, however it is sometimes on the Third Layer called "The Network Layer". Which therefore supports any packet protocol. LANs' that use switches to join segments are called 'Switched LANs' or in the case of a Ethernet Network, it maybe called  a "Switched Ethernet LAN'

This is the Second Layer in the OSI model