The tempered glass is a hardened glass, specially designed to cover and protect your mobile screen from scratches and other damages. It does not affect the screen's functionality.
In case of a fall, it does not guarantee that the screen won't also break along with it, but it provides additional protection. It features adhesive across the entire surface, unlike edge glue screen protectors that only have adhesive around the perimeter. This helps with better application and smooth touch screen operation.
It prevents dust from passing underneath, which can happen with edge glue protectors if the perimeter adhesive wears out. It is useful for modern smartphones with curved screens.