socat is a versatile and powerful command-line tool used for network communication. It stands for "SOcket CAT" and is often referred to as the "netcat on steroids" due to its extensive capabilities. 

socat allows you to create bidirectional data streams between different types of network connections, such as TCP, UDP, Unix sockets, serial ports, and more. It can also perform various transformations and manipulations on the data being transmitted.