Machine to Machine (M2M) refers to a wireless or wired network setup that allows devices of the same type and ability to communicate freely.
This type of system can be used in a variety of ways and has advanced over the last few decades with the creation of global Internet and IP network systems, facilitating enhanced and efficient communications over long distances and between large numbers of devices.
Source: https://www.techopedia.com/definition/14962/machine-to-machine-m2m