A socket is a software structure that enables communication between two devices over a network. It acts as an endpoint for sending and receiving data, allowing applications to connect and exchange information. Sockets can be used in various programming languages and are essential for creating networked applications, such as web browsers and chat programs. There are two main types of sockets: TCP sockets, which provide reliable, ordered communication, and UDP sockets, which offer faster, connectionless communication. Each type serves different purposes depending on the needs of the application, such as speed versus reliability.