A Network Interface Card (NIC) is a hardware component that connects a computer or other device to a network. Whether built into the motherboard or added as a plug-in card, a NIC provides the physical port, such as an Ethernet socket or a wireless antenna, through which data travels to and from the device. Each NIC is assigned a unique MAC address, allowing switches and routers to identify and forward network traffic correctly.
A NIC converts digital data from the computer’s memory into electrical, optical or radio signals suitable for transmission over the chosen medium, and vice versa. It implements the data-link layer protocols that package data into frames, performs error checking, and negotiates connection speed and duplex mode with its peer on the other end of the cable or link. Modern NICs often include built-in processing features, offloading tasks like checksums and packet segmentation from the CPU and may support advanced functions such as VLAN tagging, link aggregation and hardware-based encryption.
Available in wired and wireless forms, NICs range from simple 1 Gbps Ethernet adapters to multi-gigabit or fibre-optic models for data centres, as well as Wi-Fi and Bluetooth modules for mobile and IoT devices.