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Network interface card
A network interface card (NIC) is a hardware component without which a computer cannot be connected over a network. It is a circuit board installed in a computer that provides a dedicated network connection to the computer. It is also called a network interface controller, network adapter, or LAN adapter.
Purpose
- NIC allows both wired and wireless communications.
- NIC allows communications between computers connected via local area network (LAN) as well as communications over the large-scale network through Internet Protocol (IP).
- NIC is both a physical layer and a data link layer device, i.e. it provides the necessary hardware circuitry so that the physical layer processes and some data link layer processes can run on it.
Types of NIC Cards
NIC cards are of two types − 
Internal Network Cards
In internal network cards, the motherboard has a slot for the network card where it can be inserted. It requires network cables to provide network access. Internal network cards are of two types. The first type uses the Peripheral Component Interconnect (PCI) connection, while the second type uses Industry Standard Architecture (ISA). 
External Network Cards
In desktops and laptops that do not have an internal NIC, external NICs are used. External network cards are of two types: Wireless and USB based. Wireless network card needs to be inserted into the motherboard, however, no network cable is required to connect to the network. They are useful while traveling or accessing a wireless signal 