Cuboids, Rectangular Prisms and Cubes
A cuboid is a boxshaped object. It has six flat sides and all angles are right angles. And all of its faces are rectangles. It is also a prism because it has the same crosssection along a length. In fact it is a rectangular prism. 
Examples of Cuboids
Cuboids are very common in our world, from boxes to buildings we see them everywhere. You can even fit them inside other cuboids!
A box with a slot cut as a handle  Cuboids in a cuboid room  Boxes for model trains  Now that's just silly! 
Volume and Surface Area
The volume of a cuboid is found using the formula:
Volume = Length × Width × Height
Which is usually shortened to:
V = l × w × h
Or more simply:
V = lwh
Surface Area
And the surface area is found using the formula:
A = 2wl + 2lh + 2hw
Example: Find the volume and surface area of this cuboid.
V = 10×5×4 = 200 A = 2×4×5 + 2×5×10 + 2×10×4 = 40+100+80 = 220 
Square Prism

CubeIf all three lengths are equal it can be called a cube (or hexahedron) A cube is still a prism. And a cube is one of the Platonic Solids. 
 A cube is just a special case of a square prism, and
 A square prism is just a special case of a rectangular prism, and
 They are all cuboids!
Note: The name "cuboid" comes from "cube" and oid (which means "similar to, or resembling") and so indicates "it is like a cube".
Another use of oid is when we talk about the Earth being a spheroid (not exactly a sphere, but close).