The short answer
A laminated windshield consists of two or more glass layers bonded around a plastic interlayer, commonly polyvinyl butyral. When it cracks, the interlayer helps hold the assembly together. NHTSA has explained that laminated glass provides retention and energy-absorbing characteristics needed at the windshield, which is why tempered glass is not used as a conventional passenger-vehicle windshield.
Tempered glass is heat-treated to break into many relatively small pieces instead of sharp, sheet-like shards. It is commonly found in door, quarter and rear windows, although some newer vehicles use laminated side glass for sound control, security or other design reasons. The permanent marking near a corner helps identify the classification; do not decide by window location alone. Resin repair is intended for qualifying damage in laminated automotive glass. A shattered tempered window cannot be reassembled or resin-repaired and must be replaced.
