It's a curved shape that looks like a slice of a pie, with the points of the curve pointing in opposite directions.

Here's a more detailed explanation:

* Convex side: The outer curve of the crescent is convex, meaning it curves outwards.

* Concave side: The inner curve of the crescent is concave, meaning it curves inwards.

* Cusps: The points where the two curves meet are called cusps.

While the shape of a crescent moon is always curved, the precise curvature can vary depending on how much of the moon is illuminated by the sun.