Styrofoam is a brand of closed-cell extruded polystyene foam that is currently made for thermal insulation and craft applications.
In the United States and Canada, the word styrofoam refers to expanded polystyrene foam.
Syrofoam is used to make disposable items such as coffee cups, coolers, or cushioning material in packaging, which is typically white and is made of expanded polystyrene beads.
The term is used generically although it is a different material from the extruded polystyrene used for Styrofoam insulation
It is owned and manufactured by The Dow Chemical Company.(source)
So can rabbits eat styrofoam?
Unfortunately it is really bad for them to eat and there is a real risk of chokage if they chew it.
Keep it away from them.