(1) (Machine to Machine) The automatic communications between devices without any or with very little human intervention. It often refers to a system of remote sensors that is continuously transmitting data to a central system. Agricultural weather sensing, automatic meter reading and RFID tags are examples. M2M systems use proprietary networks as well as 2G cellular transmission, although 3G, 4G and LTE are also on the rise (see LTE for IoT). M2M communications is increasingly synonymous with the Internet of Things (IoT), which ties physical objects together via the Internet. See fog computing, Internet of Things and X2X.
(2) (Mobile to Mobile, Mobile to Machine) The automatic communications between mobile devices or between mobiles and other machines such as printers and hands-free vehicle systems.