What is a NIC?

A Network Interface Card (NIC) is the hardware that connects a device to a network; it carries the device's burned-in MAC address.

The NIC (Network Interface Card) is the physical bridge between a computer and the network — without one, a device simply can't talk to anything. Its core job is translation: the computer works in digital data, but the network medium carries electrical impulses, light, or radio waves, and the NIC converts between the two in both directions. It also gives the device its identity on the local network, because each NIC ships with a unique MAC (Media Access Control) address burned in at the factory.

Key points:

• Has a unique MAC address burned in, used to identify the device on the local network
• Can be wired (Ethernet) or wireless (Wi-Fi)
• Converts data to signals for transmission (and back on receipt)
• Modern devices usually have the NIC built in rather than as a separate card

Functions:

1. Encapsulates outgoing data into frames
2. Adds the source MAC address so replies can find their way back
3. Transmits and receives the physical signals
4. Performs error detection (CRC check) to catch corrupted frames

Go deeper:

• Network interface controller (Wikipedia) — connects a device to the network and stores its factory-assigned MAC address.