Known largely for its computers until then, Apple on Oct. 23, 2001, moving the company into a new era in which it would develop ever sleeker handheld devices, including the iPhone and the iPad.

After releasing Windows versions of both the iPod in 2002 and the iTunes online store in 2003, the floodgates were opened for Apple's consumer success. As points out, it was at that point that Apple became more than a niche computer maker with a cool little device. It was propelled into an iconic brand that became known across the globe for making the best music player on the market.

"From Apple's revenues to design influence to the fundamental business and distribution models that glue the industry together, the iPod started it all," writes Mike Elgan.

The iPod also changed the music industry.

Remember when you'd have to buy an entire album for more than $10 just to get one song? The iTunes store changed all that when it let people buy and download to their iPods individual songs for less than $1. Today the amount of content Apple sells there in addition to music -- movies, TV shows, apps, books and more -- is a massive asset for the company and one that propels people to continue buying its devices in droves.