The Corning Museum of Glass says:
Glass is a rigid material formed by heating a mixture of dry materials to a viscous state, then cooling the ingredients fast enough to prevent a regular crystalline structure. As the glass cools, the atoms become locked in a disordered state like a liquid before they can form into the perfect crystal arrangement of a solid. Being neither a liquid nor a solid, but sharing the qualities of both, glass is its own state of matter.
Glass is made with Silicone Dioxide, found in sand, Potash, and Calcium Oxide and mixing them together under high heat. The addition of metallic oxides, such as iron or copper gives the glass its color.
Tempered glass and Laminated glass are types of Safety glass. Certain building codes require the use of safety glass in locations where breaking glass could be dangerous to passers by.