Wikipedia has a pretty good definition for starters. An excerpt retrieved today:
In this blog, I’m focusing specifically on what can be accomplished with microcontrollers and single-board computers, inexpensive devices that can process real world inputs with simple software, and ouput some really amazing, dynamic processes.
Really, ‘physical computing’ is a fancy name for what I’ve been trying unsuccessfully to do with electronics for years. To me, it represents automation plus innovation, minus the perspiration. The ability to hack my house, my appliances, my car, my stuff. The ability to build features into my devices that weren’t part of the manufacturers design.
This means I can be a maker, not just a consumer.
I hope you enjoy reading this blog and I hope that you get yourself a microcontroller board too.