How does inertia affect the motion of an object?

Inertia affects the motion of an object as follows:

When an object is in motion, it will continue to be in the same state unless otherwise some outside force is being applied to it. Thus, inertia affects the motion of an object. It restricts some other force being acted upon the object.

But mass of an object is directly proportional to inertia. So when the inertia is more on an object, it means that the object has more mass. For example, if there are two similar bricks, one that is made up of mortar and the other one is made of Styrofoam.

To identify which brick is made of Styrofoam without lifting the bricks, push both the bricks with equal force, the one that has less resistance tends to move faster. This means that it has less inertia and hence less mass.