Ethernet Controllers

Ethernet controllers are an integrated circuit chip that control Ethernet communications. Ethernet is how most computers communicate with each other and is also how most computers connect with the Internet. The internet cable, which plugs into your computer, transfers data to the Ethernet controller, which then decodes the data and puts it into a form your computer can use.
An Ethernet controller determines whether each packet of data is meant for the local computer or another computer on the same network. If the information is meant for the local computer, it decodes that information and relays it to the processor. If the information is meant for another computer on the network, the information is discarded.
Applications
Modern computers have built-in Ethernet controllers on the motherboard. Older computers use a network interface card, which has the Ethernet controller chip on it.