Here’s a quick video on how tempered glass will shatter into hundreds of small pieces. These pieces have smaller mass so they are less likely to cause severe injury compared to shards from traditional glass.
This video explains and shows the difference in the tempered glass and traditional glass when they break. Notice that they need to add more energy to the hammer to break the tempered glass!
And if you are really curious how all this translates into a real life situation, here’s a good demonstration of a tempered glass shower door being broken on purpose. Before you watch, think first of a traditional glass and how easy they are to break it. That’s what the person in the video had in mind when first attempting to break his tempered glass shower.