The glockenspiel is basically a xylophone with metal bars instead of wooden bars. Metal, being denser than wood, creates a higher pitch, so the resulting pitch range is higher than the typical xylophone.
Each bar is pretuned during manufacturing according to the desired pitch. A soundbox increases loudness. The bars are typically played with sticks, usually with hard balls on their tips.
Source: http://en.wikipedia.org/wiki/Glockenspiel-w.htm
Source: http://en.wikipedia.org/wiki/Glockenspiel-w.htm
http://www.beginband.com/sndclips.shtml (bells)