Stained glass is a composition of glass pieces. These can be white or colored and can be decorated. The word stained glass refers to a technique, while the closing of a fixed window with glass is called a skylight.

Created in the early Middle Ages, these pieces are assembled by lead rods, also called "lead". This process, although still dominant today, is not the only one in use: other techniques, such as copper tape (also known as the Tiffany method, after its designer Louis Comfort Tiffany), glass slabs embedded in concrete or silicone, gluing (with resins or polymers), thermoforming, fusing and free-glass stained glass, can be used or combined.

A stained glass window is called vitrerie when its design is geometrical and repetitive (for example lozenges or bounds). Stained glass is generally clear and unpainted.
>Interesting link to the website of the international stained glass center of Chartres