Over the years Corning has made it their mission to make the most durable glass for cellular devices. They have come a long way since the first devices however Glass still breaks when you drop your phone. Gorilla Glass 4 was Corning's first attempt at building glass durable enough to handle drops onto rough surfaces. The next iteration looks to improve further in this specific category.
According to Corning the new Gorilla Glass 5 will survive a 5 foot drop onto rough surfaces (ie sandpaper for their tetsing) 80% of the time. This means 4 out of 5 drops will survive. Gorilla Glass 4 while more durable when it comes to drops was also the most scratch prone glass I have ever used. I have right now 3 nasty deep scratches in which I have no clue how they got there. I am hoping that Gorilla Glass 5 will also improve on the scratch resistance.