Any device that is going to connect to a network, needs a network interface card (NIC). Servers, printers, routers, switches, tablets, phones, etc. could all have network interface cards.
A NIC must be specific to the type of network you’re connecting to. For example, if you’re connecting to an Ethernet network you need an Ethernet NIC. Similarly, if you are connecting to a wireless network, you’d need a wireless NIC. If connecting to multiple types of networks, then you’ll need multiple NICs.
NICs can be added as an expansion card or they can be build in to the motherboard.
There are many types of NICs: single port, multi-port, copper, fiber, etc.