"A switch is a device in a computer network that electrically and logically connects together other devices. Multiple data cables are plugged into a switch to enable communication between different networked devices. Switches manage the flow of data across a network by transmitting a received message only to the one or more devices for which the message was intended. Each networked device connected to a switch can be identified using a MAC address, allowing the switch to regulate the flow of traffic. This maximizes the security and efficiency of the network."
The core of your network's performace depends largely on the quality of your network switching infrastructure. Different switches have different features, functions, speed and most importantly 'throughput'. This is the amount of data that can be moved from one port to another at any given time. Choosing the right switch for your application can be the deciding factor between success or failure.