What do you mean by mass element $dm$?

(N/A) In physics,a mass element $dm$ refers to an infinitesimally small portion of a continuous body's total mass $M$.
When dealing with objects that have a continuous distribution of mass (like a rod,a disc,or a sphere),we cannot sum the individual particles as we do in a system of discrete particles.
Instead,we divide the body into an infinite number of such tiny elements $dm$.
The total mass $M$ of the object is then calculated by integrating these elements over the entire volume,area,or length of the body: $M = \int dm$.
This concept is fundamental in calculating the center of mass,moment of inertia,and gravitational potential of continuous bodies.