Safety glass is a type of glass which is designed to resist breaking, and to break in a way which minimizes the risk of injuries in the event that the glass cannot withstand the forces which are exerted on it. Car windows are classically made from safety glass to promote safety in collisions, and this type of glass can also be used in regular house windows, eyeglasses, laboratory glassware, and a wide variety of other products. As its name would seem to imply, safety glass is meant to be safer than ordinary glass.
There are two ways in which safety glass can work: tempering or laminating. Tempered glass is made by treating the glass very carefully as it is heated and cooled to increase its tensile strength, making it hard to break. If tempered glass does break, it snaps apart into rounded chunks, rather than breaking up into jagged pieces which could potentially be very dangerous. People who have seen a broken side window in a car have probably seen an example of tempered safety glass.