There are three types of inertia:
(i) Inertia of rest: When the object is at rest relative to its surroundings then it is called inertia of rest. This situation can be changed only by applying external force, e.g., if an object kept in a house remains at the same place for days or years unless someone moves it from its position by applying force, it is an example of inertia of rest.
(ii) Inertia of motion: When an object is moved on a frictionless surface or thrown into a vacuum, it will continue to move on its original path unless an external force is applied. In real situation, air or floor etc. create friction on a moving object hence we are not able to see frictionless motion. This type of inertia in which the object keeps moving is called the inertia of motion.
(iii) Inertia of direction: In the above example, we see that unless an external force acts, the object or particle keeps moving in its direction. This property of motion is called inertia of direction.