Networking devices:


Hub:
Hub is a Physical layer device that provides a logical bus structure for ethernet, Hub will take physical layer from one interface and replicate that signals on all of its other interface.
Bridge:
A bridge solves layer-2 bandwidth and collision problems. it performs its switching function in software and supports only half-duplex connections. it typically supports 2-16 ports and performs store and forward switching.

Switch:
Switch is a layer2(datalink) device that is used to solve bandwidth and collision problems, switch perform there switching in hardware called ASIC(Aplication specific integrated circuit). All switches support store and forward switching some switches also support cut-through and fragment free switching. All switched typically support both half duplex and fullduplex. switch comes in many sizes, some one have more than hundred ports.

Router:
Router is a layer3(network) device. router is used to connect different types of network provide internetworking. router perform the following functions. define logical addressing schemes, contain broadcasts and multicasts, find layer-3 paths to destinations, connect defferent media types, switch packets on the same interface using VLANs, and use advanced features such as filtering and Quality of Service.
Gateway:
A gateway is a network point that acts as an entrance to another network.
VLAN:
To segment layer 2 broadcast domain.