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. When a hub receives a packet (chunk) of data (a frame in Ethernet lingo) at one of its ports from a PC on the network, it transmits (repeats) the packet to all of its ports and, thus, to all of the other PCs on the network.  If two or more PCs on the network try to send packets at the same time a collision is said to occur.  When that happens all of the PCs have to go though a routine to resolve the conflict.  The process is prescribed in the Ethernet Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol.  Each Ethernet Adapter has both a receiver and a transmitter. A hub is a device that attaches multiple computers on an Ethernet network. If you 
have a number different computers that you want to connect together, you could connect each to the hub. Any packet that is sent out by any computer on the network will immediately be transmitted to the other computers. Each computer will determine if the packet was really intended for it, and filter out packets that were  intended for other computers. Network switch is a marketing term rather than a technical one. Switches may operate at one or more OSI layers, including physical, data link, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch, although use of the term is diminishing.

                Modern network hardware operates on the “Open System Interconnection” (OSI) standard. This standard defines how communications on a network should be implemented. By conforming to this standard, modules from different manufacturers can coexist on the same network. Wireless networks (WiFi) and the 802.11X standard are an additional subset of network systems. When a message is sent between computers, it is broken into parts. At the base level, the message is reduced to “1″ and “0″ bits. The next level is a group of bits called a “frame”.

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