Volume
Volume is the measure of the amount of space inside of a solid (3dimensional) figure,
like a cube, sphere, cylinder or
pyramid.
It's units are always "cubic" somethings, that is, the
number of little element cubes that fit inside the figure.
The formula for the volume of a rectangular prism is:
Area = L x W x H
where:
L = length
W = width
H = height
For example, the volume of a shoe box (a
parallelepiped) that is
4 inches by 6 inches by 12 inches is 4 x 6 x 12 = 288 cubic inches.
This means that it would take 288 little 1inch cubes to fill the shoe box.
Here are the formulas for the volume of some common 3D shapes:
Sphere 

V = 4 R^{3} / 3 where R is the radius of the sphere 
Pyramid 

V = (L W H) / 3 where L = base length, W = base width, H = pyramid height 
Cylinder 

V = L R^{2} where L is the length of the cylinder and R is the radius of the end circle 
Cone 

V = H R^{2} / 3 where H = the cone's height and R is the radius of the base 
