Inertia is the resistance of motion of an object. The more inertia, the
harder it is to move something. The less inertia, the easier it is to
move. Take a bowling ball and a marble. The marble can be flicked by the
finger, because it has less inertia. The bowling ball takes the entire
hand because it has more inertia than the marble.
According to Newton's laws, an object that is moving tends to continue
in motion. A moving object has inertia as it has Mass and Velocity. An
object that is not moving requires a Force exerted on the Mass to start