What is Newton's first law of motion?

Newton's First Law (Law of Inertia): An object at rest stays at rest, and an object in motion stays in uniform motion in a straight line, unless acted on by an external unbalanced force.

Inertia: The natural tendency to resist any change in motion state.

Real-life examples: Book lying on a table; passengers lurching forward when a bus brakes; dust flying off a beaten carpet.

Newton's First Law says objects resist any change in their motion state unless an external unbalanced force acts on them.