1) A device used to breakup light into its component colors; different elements can be identified by the different colors found with in this source of light.
2) A spectroscope is a device that lets us find out what things are made of. It works by taking light and splitting it up into its component colors.
Different elements make different colors when they glow. We can make objects and gasses glow by heating them up in a flame, or by passing electricity through them.
The spectroscope spreads out the colors of the light, and we can identify the elements by the bright lines we see in the spectroscope.
How to build a simple Spectroscope
source: www.ScienceToys