Net Force

Net force is the overall force of an object.

If the net force is zero then the force is balanced because the speed remains the same.

If the net force is not zero then the forces are unbalanced because of the change in speed, direction, or both

When a unbalanced force is put against an object the it has acceleration

Friction is the act of force to the opposite direction that the object is moving. Friction will cause an object to slow down and eventually stop.

Velocity is the speed of something in a given direction.

Examples
If you want to see how fast your car goes against the wind then you can use net force.
If your buying tires you may want to see how much friction the tire has.