A tempered glass protector is a multi-layered screen protector. It has a bottom layer of absorbent silicon, PET film and an optically clear adhesive tempered glass and oleophobic coating in that order. Tempered glass is up to five times stronger than normal glass.
Tempered glass is made by controlled chemical and thermal treatments to increase its strength. The glass is first first heated and then rapidly cooled with help of blowers. One surface gets cooled much faster thus putting it in compression and the other surface in tension. This difference makes the glass 5 to 10 times more stronger than it was in the first place. All the technical jargon apart, you can buy one for all popular smartphones from all leading online stores for a nominal charge.