Bubbles are a pocket of air surrounded by a thin coating of something else. Bubbles are usually made from blowing air into soapy water. They are round, and float through the air. There are pretty colours on the surface of the bubble.
Rubble is broken parts of a building, either leftovers from making the building or as a result of the building being knocked down. ruins are typically surrounded by rubble.
Stubble is the short stalks left when a crop like wheat has been harvested. Stubble is also used to describe other things that look like grain stubble, like the short hair on a man'schin that you can see a little while after he has shaved.
