The area of a shape or space is the amount of space inside it. This applies to only two dimensional (flat) shapes. If we are dealing with a three dimensional shape, the space inside this is called the volume. Since perimeter is the measure of a length, the units it is measured in are cm, m, km etc.
As area is a measure of space rather than distance, it is measured in square units. This could be square metres, square centimetres, square feet and so on. You will often see these written as cm2, m2, ft2, etc. Over the next few pages you will learn how to find the area of simple shapes, compound shapes and circles.