Area is a measure of how much space there is on a flat surface,
For example: the size of an apartment is 150 square feet, or a piece of land is 1250 square meters, or the area of Canada is 9,984,670 square kilometers. In all of these examples we talk about area.
For example two sheets of paper have twice the area of a single sheet, because there is twice as much space to write on.
On the other hand area is measured by the number of square units that cover a closed figure. Area is measured in square units.
The area of this square is 16 square units.
That means 16 square units are needed to cover the surface within the square. We can use different square units. For example, a square meter is a square with all sides that are one meter in length. In the same way, a square foot is a square with all sides that are one foot in length.
There is a shorthand way of writing a square unit. We write the letter(s) for the unit with a superscript 2 after it, like this:
8 square meters is written as 8 m²
8 square feet is written as 8 ft²