Ordinary glass is quite useful, but it has its limitations. For example, it is quite fragile. With just a little pressure it can shatter, exploding into sharp shards that can hurt anyone in its vicinity. It is also quite vulnerable to extreme heat or cold, and can crack if placed in these temperatures.
To solve this companies manufacture tempered glass. This is considered a “safety glass” and is preferred in situations where ordinary glass could break or shatter. Aside from being up to five times stronger, if it does shatter, the shards are usually small and rounded, like pebbles. There are no sharp edges that can cut a person.
Tempered glass is much more durable because it is exposed early on to extreme heat and rapid cooling, creating a harder and more “stable” material. This is why buildings will use tempered glass—if the kid next door accidentally throws a ball against a window pane, at least it will only crack (as opposed to shattering and hurting anyone who happens to be sitting next to it). Computer screens and shower doors are also built with tempered glass, also with the user’s safety in mind. Car windows, in particular, used tempered glass for the back and side windows. However, windshield are actually made of glass that is laminated on both sides with plastic. The plastic adds as another layer of protection, “catching” any glass that may crack or break off upon impact.
Tempered glass is also resistant to heat. That is why tempered glass is used in making appliances, like microwave oven windows, or the coffee pots in percolators.