Stained glass refers to glass that has been coloured by adding metallic salts during the manufacturing process.
Often an artist will add finer details such as shadows or outlines. This is done using a metal oxide paint. The paint is fused to the glass by heating in a kiln.
Learning more about Stained Glass:
www.stainedglassmuseum.com
Stained Glass Tutorials
Florida University course on Stained Glass