Question

what is magnitude in motion?

Answer 1

, magnitude means greatness of size or extent.
A vector has a magnitude and a direction, its magnitude being the numerical value of its length, size or quantity.
A scalar in physics is defined by magnitude or quantity and not by direction.
Mass, charge, volume, time, speed, temperature are examples of scalars with magnitude.
The magnitude of a physical quantity is usually given by a number with a certain unit.

Answer 2

A magnitude is a non negative real number associated with some physical entity. It is used a simplified representation of a more complex situation.