A network adapter is a hardware device that enables a computer to connect to a network, such as the internet or a local area network (LAN). It allows the computer to send and receive data by converting digital data into signals that can be transmitted over network cables or wireless connections, and then converting incoming signals back into usable data. Network adapters can be wired (Ethernet) or wireless (Wi-Fi), and they are essential for communication between computers and other devices on a network.