I'm not real sure about a defn. in this problem and need some clarification.

The problem reads..

"The universe is all Real #'s. Let A be the closed interval [0,2] and let B be the closed interval [-1,1]. Find A\B, etc etc."

My question is this: Byclosed interval, does this mean (for A) that the set is all real #'s between (and including) zero and two? And if not, what does it mean?

Thanx!