A (possibly unbounded) box in R^n. Specifically, a Box represents the Cartesian product of n closed intervals. Each interval has the form of one of [a, b], (-oo, b], [a, oo), or (-oo, oo). E.g. low = [-oo, -oo], high=[oo,oo] is a 2D Cartesian plane
The Discrete space allows a fixed range of non-negative numbers, so in this case valid actions are either 0 or 1.