Laminated glass is manufactured by bonding two or more layers of glass together with layers of PVB, under heat and pressure, to create a single sheet of glass. When broken, the PVB interlayer keeps the layers of glass bonded and prevents it from breaking apart. The interlayer can also give the glass a higher sound insulation rating.
There are several types of laminated glasses manufactured using different types of glass and interlayers which produce different results when broken.