If you have a vague idea about the Internet of Things, or would prefer to learn by osmosis, then have a look at the post on Enchanted Objects for some background, and the OpenIoT showcase to see some examples of real things people are making.
Here's an executive summary, hope it helps!
A computer processor such as the 486 used to cost around the same as a small car. Nowadays a chip with similar power is the price of a chocolate bar.
When processing power is so cheap, you can afford to put them in places that you couldn't before. Not just a business workstation, or a home PC, but also a telephone, an electricity meter, a bedside lamp, or a teddy bear. We can make objects intelligent. We can make them think, and speak. In short, we can make magical things, Enchanted Objects.
In this book we will look at the kind of computer chips that can be embedded in objects ("microcontrollers" such as the Arduino) and take you through each step of the process from prototyping a Thing, to manufacturing and selling it.