A hypercube is just the higher-dimensional analog of a cube. A 2-hypercube is a square, a 3-hypercube is a cube, and so on.

Edit: I know complaining about downvotes is against the rules, and I’m not complaining, because I really don’t care about my karma on this site — but I am really confused and curious how people could possibly be opposed to me explaining a mathematical concept to someone who expressed frustration at not knowing it.