A rather simplistic answer is: A cube or cuboid shape has (usually) 2 sides, 2 ends, 1 top and 1 bottom.
A hexahedron has a triangular pyramid on top and on bottom and share the bases.
okay here is the difrence a cuboid is a shape that is 3D and has eight faces a cylinder however is a 3D shape but it only has 2 faces the top and the bottom face
A hexahedron is the name for a 6 sided 3D shape.
A nonagon is a 2D shape and there is not a 3D equivalent shape.
the name of a 20 sided 3d shape is called a icosahedron
A cuboid is a 3D shape that can be a cube or a rectangle, both having 2 ends, 2 sides, and a top and a bottom face.