What is the difference between inertia and friction ? 

Inertia is defined as the property of a body to continue to be at rest or in uniform motion until it is disturbed by an external force. While friction is defined as the force that always opposes the relative motion between two surfaces.

Inertia will cause a body to move until a force is applied to stop it. While friction will always try to bring a moving body to a halt.

Inertia is measured in terms of mass, i.e. kilogram. While friction is measured in terms of Newton.