The first moment of area represents the distribution area over a rotational axis.
It is used for finding centroid, its unit is a cubic meter.
The second moment of area represents the dispersion of points around an arbitrary axis.
The first moment of area is based on the metric space mathematical construct moments. It's a measurement of a shape's spatial distribution in regard to an axis.
The sum over all the tiny portions of the form of the area of that section times its distance from the axis [ad] is the initial moment of area of a shape about a specific axis.
The centroid of an area is frequently determined using the first instant of area.
The area moment of inertia, also known as the second moment of area, or second area moment, or quadratic moment of area, is a geometrical feature of an area that represents how its points are distributed with respect to an arbitrary axis.