An Ethernet switch is a networking device that connects multiple devices within a local area network (LAN). It uses packet switching to receive, process, and forward data to the correct destination device. This helps improve network efficiency by reducing data collisions and ensuring that data packets reach their intended recipients quickly. Ethernet switches operate at the data link layer of the OSI model and can support various speeds, such as 10/100/1000 Mbps. They typically have multiple ports, allowing several devices, like computers and printers, to communicate with each other simultaneously, enhancing overall network performance.