Machine-to-Machine (M2M) can include a device (such as a sensor or meter) to capture an event (such as temperature, status [on/off], pressure, etc.), which is then relayed through a network (wireless, wired or hybrid) to an application (software, more likely on a cloud), and finally translates the captured event into meaningful information for the user.
M2M and IoT are part and parcel of one another. When it comes to Internet of Things (IoT), M2M is what gives it wheels. Through wireless M2M connections, the possibilities of monitoring and reporting device states and gaining new insights on efficiency of various systems are endless.