Glass  is what windows, copa, vaso, jarra, tubo are made of; Vidrio ; cristal 

These words can cause confusions because:

a cup – is a taza (except in sports copa)

glass of wine – copa or vaso

cup of coffee – when your coffee comes in a small glass

glass cup of coffee – when it has a handle to hold it

plastic glass – is the copa de plástico which you sometimes use for wine

Vase – is the thing you use to put flowers in

Jar – is a glass container for jam

Tube – is a container of tootpaste

Glasses  (always plural)- are the things that people wear to help them see well. Each piece of glass is the lens and they are held in a frame.