What is the different type of networking / internetworking devices?

Repeater:

Also called a regenerator, it is an electronic device that operates only at physical layer. It takes the signal in the network before it becomes weak, regenerates the original bit pattern and gets the refreshed copy back in to the link.

Bridges:

These operate both in the physical and data link layers of LANs of similar type. They separate a larger network in to smaller segments. They have logic that permit them to keep the traffic for each segment separate and therefore are repeaters that relay a frame only the side of the segment having the intended recipient and control congestion.

Routers:

They relay packets between multiple interconnected networks (i.e. LANs of dissimilar type). They operate in the physical, data link and network layers. They had software that enables them to determine which of the various possible paths is the best for a particular transmission. Gateways: They relay packets among networks that have different protocols (e.g. among a LAN and a WAN). They accept a packet formatted for one protocol and change it to a packet formatted for another protocol before forwarding it. They operate in all seven layers of the OSI model.