Pressed glass is a way of making fancy cups, plates, and other things that you might use to fancy up your dinner table or decorate your house. Basically, a grown-up uses a special machine to squish liquid glass into a mold to make a pretty design.
It's kind of like when you play with play dough and use a cookie cutter to make fun shapes, but instead of play dough, it's very hot and sticky glass! Once the glass is squished into the mold, it cools down and hardens to make a fancy design that you can use to drink from or eat off of.
People have been using this method to make fancy glass things since the 1800s, and it's still popular today!