What does inertia apply to?

Inertia is a fundamental property of all objects having mass. Mass resists the change in motion. Inertia applies to both the states of a body i.e., body at rest and at motion. Inertia is applicable to all objects in everyday life. For example " your body will continue to move forward because of inertia, when suddenly brake are applied during driving"

Inertia is generally given by Newton's first law of motion, which is also called as "the law of inertia". This law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. The more massive an object is, the greater will be its inertia, meaning that s it will require more force to change its state of motion.