NIC Network Interface Card
The hardware connecting a machine to the network, and the holder of its MAC address.
These days almost always integrated into the motherboard. Modern cards do considerably more than move bits: checksum calculation, segmentation (TSO/LRO), RSS to spread interrupts across cores, and SR-IOV to present themselves as several virtual cards to VMs.
At the far end of the scale sit SmartNICs and DPUs, which run the entire network stack — encryption and virtual switches included — on the card's own processor cores to offload the host.