The iPod is ten years old, and in that short time, the concept of a multi-function device that fits in your pocket has transformed the way we work and play--not necessarily always for the better. There were other pocket size music devices before the iPod, but Apple provided easy to use software (iTunes) with an easy to use interface on the iPod itself that lent itself to rapid and easy browsing of your music library.
The original iPod had a 5 Gig hard drive--an actual rotating device, that was replaced in just a few years with solid state hard drives with no moving parts and much lower power consumption for longer battery life. The iPod led directly to the iPhone, which has largely rendered stand along music players obsolete--Apple only offers one iPod model now--the iPod Touch.
Here is the first commercial for the iPod.