Area is a measure of a region on a surface. Area is usually found by multiplying length and width, and units can be square meters (m²), square centimeters (cm²), square inches (in²), or square feet (ft²).

The area of a rectangle or square is calculated by multiplying its length and width. For example, the area of a rectangle with a length of 3 meters and a width of 2 meters is 3 x 2 = 6 square meters.

The area of a triangle is calculated based on the base and the height of the triangle. For example, if the base of a triangle is 5 cm and the height is 3 cm, the area is (base*height)/2 = (5*3)/2 = 7.5 cm². (This formula is only valid for a straight triangle. If the base and height of a triangle are not measurable, other methods can also be used to calculate its area. For example, if we know the two sides and angles of a triangle, we can use Heron's formula to calculate its area.)

The area of a circle is calculated by multiplying the square of the radius of the circle with pi. The pi number is considered to be 3.14159265358979323846 and is usually used as 3.14 to calculate the area of a circle. For example, if the radius of a circle is 5 cm, the area is pi*(radius^2) = 3.14*(5^2) = 78.5 cm².