Modbus is a communication protocol used in industrial automation systems. It allows devices like sensors, controllers, and computers to exchange information over a network. Developed in the late 1970s, it is widely used due to its simplicity and reliability. The protocol operates in a master-slave configuration, where one device (the master) controls the communication and multiple devices (the slaves) respond to requests. Modbus can be implemented over various physical layers, including RS-485 and TCP/IP, making it versatile for different applications in industries such as manufacturing and energy management.