A robe is a loose piece of clothing that you might wear over your pajamas or put on when you get out of the shower. Most robes tie around the waist with a fabric belt.
There are dressier types of robes as well, like the ceremonial robes a judge wears in a courtroom or the elegant robes worn by a queen on a formal occasion. You can also use robe a verb, meaning "to dress or clothe," or literally "to put on a robe." Robe shares a Germanic root with rob, most likely from the idea that robbers would "take garments from the enemy as spoils or booty."