A network card, also known as a network interface card (NIC), is a hardware component that allows a computer or device to connect to a network. It can be wired, using an Ethernet cable, or wireless, using Wi-Fi technology. The network card converts data from the computer into a format suitable for transmission over the network and vice versa. Network cards are essential for communication between devices, enabling activities like browsing the internet, sharing files, and accessing printers. They come in various forms, including internal cards that fit into a computer's motherboard and external USB adapters. Ethernet, Wi-Fi, and data transmission are key concepts related to network cards.