Apple ipod

iPod is a brand of portable media player designed and marketed by Apple Computer and launched in 2001.   Recent iPods are designed around a central scroll wheel — although the iPod shuffle has buttons only. The full-sized model stores media on an internal hard drive, while the other models use flash memory, allowing for a physically smaller size. The most expensive iPods can hold audio, photos, movies, and games, though most are used primarily as music players, which is the originally intended design function. Like many digital audio players, iPods can also serve as external data storage devices, holding any file type. 

which are the other similar products in the market? 

1. Zune of microsoft: http://en.wikipedia.org/wiki/Zune 

2.  Zen Vision:M of Creative

http://en.wikipedia.org/wiki/Creative_Zen#Zen_Vision:M