Borosilicate glass, such as this PYREX,jug (back), can withstand extreme changes of temperature, unlike normal glass (front), which shatters. The ordinary glass jar at the front is quite a bit thinner and considerably lighter. You can also see, very clearly that the borosilicate glass is a slightly blueish color (as is the boron oxide from which it's made).
Once the sand is melted, it is either poured into molds to make bottles, glasses, and other containers, or "floated" (poured on top of a big vat of molten tin metal) to make perfectly flat sheets of glass for windows. Unusual glass containers are still sometimes made by "blowing" them. A "gob" (lump) of molten glass is wrapped around an open pipe, which is slowly rotated. Air is blown through the pipe's open end, causing the glass to blow up like a balloon. With skillful blowing and turning, all kinds of amazing shapes can be made.