The SMC EtherPower II 10/100 Ethernet Adapter is a network interface card (NIC) that allows a computer to connect to a local area network (LAN) via Ethernet. This adapter supports both 10 Mbps and 100 Mbps Ethernet speeds, enabling fast wired connections for network communication, file sharing, and internet access. It was commonly used in older desktop computers, particularly in the late 1990s and early 2000s.