The Internet of Things concept is neither entirely new nor is a futuristic distant technology. It is being built today with today's technology, and you can find it in some of your own home devices, big data clouds, and sensors. It started with wireless technologies converging progressively with micro-electromechanical systems (MEMS) and the Internet.
The initial concept suggested that it were the persons who should share the data. Today, it can be defined as a network of sensing and actuating devices with the ability to share information.
The first time the term "Internet of Things" was officially used in a publication back in 1999, where Kevin Ashton published his vision in the RFID Journal:
You can't eat bits, burn them to stay warm or put them in your gas tank. Ideas and information are important, but things matter much more. Yet today's information technology is so dependent on data originated by people that our computers know more about ideas than things. If we had computers that knew everything there was to know about things—using data they gathered without any help from us—we would be able to track and count everything, and greatly reduce waste, loss and cost. We would know when things needed replacing, repairing or recalling, and whether they were fresh or past their best. The Internet of Things has the potential to change the world, just as the Internet did. Maybe even more so.
As you can see, devices sharing data is the real concept behind IoT. Such devices could either be living or inanimate. A Thing in the IoT context can be a person wearing a pulse monitor, a dog carrying a tracking device, a garbage bin that notifies it needs to be emptied, or a thermostat that adjust itself automatically to help you lower your electricity bills.
IoT assumes that Things must be uniquely identifiable and able to gather data recurring to sensors. They must also have the ability to communicate and transfer data over a network. Such data could be used for monitoring purposes, big data processing, or even to control that same Thing.
Things supporting this machine-to-machine communication are usually known as smart devices. An example of a smart device is the famous Google Nest thermostat (https://nest.com/thermostat). Being more than a simple thermostat, it shares its usage data to help you save on your home's energy, while keeping you cozy. It can also work together with other smart devices such as some Mercedes-Benz cars (https://nest.com/works-with-nest/). The car GPS system shares data with the Nest cloud, making it possible to start heating or cooling your home, based on the expected arrival time.