It refers to the communication between machines. A machine can be an electronic device, a robot, a car, an industrial motor, anything that is not a person. That machine has to communicate over the Internet with a server. This server manages the information related to the machine and manipulates it remotely. The communication between the machine and the server is done by different means such as Ethernet (a LAN connection), an Wireless, GPRS, a radio link or a satellite.