What do Hogwarts robes look like and do you wear clothes underneath?

Hogwarts robes are black, work robes and yes you do where clothes underneath them! They have a button thing about 5/6 of the way up, they have big sleeves and should be long enough to cover your ankles. In the books, many students get them tailor made at Madame Malkins Robes for all Occasions. I also think that they have the school crest on the right side of the button and have big pockets just below waist height.