Area vs Length

Area is measured in square units, such as square inches, square centimeters, etc.  These units can be thought of as little squares that are 1 unit on a side, and area is a measure of how many of these units will fit inside a closed region.  Of course, we sometimes have to think of fractions of these units.  Length, on the other hand, is a "linear measure" and can be thought of as the number of "unit segments" that can be placed along a line or curve.  For example, a rectangle that measures 3 cm by 5 cm has an area of 15 square centimeters and a perimeter (which is a linear measure) of 16 cm:

When we speak of the area of a three-dimensional solid, we usually mean the total surface area.  Sometimes this can be found by constructing a net and adding the areas of each part of the net.  In any case, the concept of area is the same and is a measure of the number of square units that can cover the surface of the object.

When converting between different units, do not confuse linear conversions with area conversions.  For example, a foot is equal to 12 inches, but a square foot is not equal to 12 square inches, because a square that is 1 foot on each side contains 144 square inches: