A part of the plane enclosed by a simple closed figure is called a plane region and the measurement of it, is called its area. The area is measured in square units. The length of the boundary of a closed figure is called the perimeter. The units of the perimeter are same as that of length, i.e., m, cm, mm, etc.
The area of a circle is the number of square units inside that circle. If each square in the circle to the left has an area of 1 cm2, you could count the total number of squares to get the area of this circle. Thus, if there were a total of 28.26 squares, the area of this circle would be 28.26 cm2.