Tempered glass is a kind of safety glass regularly used in applications in which standard glass could pose a potential danger. Tempered glass is four to five times stronger than standard glass and does not break into sharp shards when it fails. Tempered glass is manufactured through a process of extreme heating and rapid cooling, making it harder than normal glass.
The brittle nature of tempered glass causes it to shatter into small oval-shaped pebbles when broken. This eliminates the danger of sharp edges. Due to this property, along with its strength, tempered glass is often referred to as safety glass.
Toughened glass has two advantages over regular glass -- when it breaks, and when it doesn't. Because toughened glass is created with uneven heating that causes the cooling glass to form layers instead of a solid sheet, it is much more resistant to impact than "annealed" glass. It isn't indestructible, but when it does give way, this glass comes apart in a spray of cube-like pellets rather than jagged shards.