A network interface card (also known as a NIC, network card, or network interface controller) is an electronic device that connects a computer to a computer network , usually a LAN. It is considered a piece of computer hardware. Most modern computers support an internal network interface controller embedded in the motherboard directly rather than provided as an external component.
Network cards let a computer exchange data with a network. To achieve the connection, network cards use a suitable protocol, for example CSMA/CD. Network cards usually implement the first two layers of the OSI model, that is the physical layer, and the data link layer. There are older network protocols such as ARCNET, introduced in 1977, LocalTalk or Token Ring, but today, most network cards use Ethernet.

Ethernet cards are available in several different standard packages called form factors that have evolved over the last several generations of PC hardware:

Ethernet cards operate at different network speeds depending on the protocol standard they support.
Old Ethernet cards were capable only of the 10 Mb/s maximum speed originally offered by the Ethernet standard. Modern Ethernet adapters support the 100 Mb/s fast Ethernet standard and an increasing number now also offer Gigabit Ethernet support at 1 Gb/s (1000 Mb/s).
Ethernet cards ruled when cables remained the primary form of network access. Although Ethernet offers more reliable connections than wireless networking and therefore remains popular as a built-in option for desktop PCs and other relatively immobile computers, mobile devices including laptops and tablets have shifted away from Ethernet and toward Wi-Fi. The expansion of Wi-Fi services in workplaces, coffee shops, libraries and other public places has reduced the need for Ethernet cards.