To fully understand the Internet of Things, you will need to become familiar with the electronic components that make things 'smart'. This include microprocessors such as the Arduino or Particle devices. These are just two examples of the range of devices available, but they provide a good introduction to the concepts needed.
You will also need a basic understanding of the sensors and actuators that can be connected to a microprocessor in order to collect data from the environment, or have some physical effect on it.
All this, of course, assumes that you know a little about electricity and circuits. If you do not already have a basic understanding of electronics, the introduction on the Processing web site is well worth a visit. The rest of the pages in this section describe some particularly useful concepts and how to use them.