Question

What is the difference between: first moment of area and second moment of area?

Answer 1

when you talk about moment of inertia with respect to a particular point and the point of application of force it is first moment of inertia and when you talk about moment of inertia with respect to the axis of rotation you are finding second moment of inertia

First moment of area is commonly used in applications to determine the centroid of an object.

The second moment of area, is a property of a shape that is used to predict its resistance to bending and deflection which are directly proportional.