The meaning of the area is the measurement of a surface in this case a circle, which can be find by using the formula A=πr^2, where r is equal to the radius of the circle.
On this exercise is given that a circle has a diameter of 10cm and it is asked to find its area, as previous said the only way to find the area of a circle is to use the formula A=πr^2, but on this case the radius is not given. As result you have to divide the measurement of the diameter by two, and the number found represents the radius.
10cm/2= 5cm The radius of the circle is 5cm.
Now that the radius is known you can substitute the values in the formula to find the area of the circle.
A=πr^2
A=(3.14)(5)^2
A=(3.14)(25)
A=78.5 cm^2
The area of the circle is 78.5 square centimeters.