Balanced force: If the net force of several forces acting on a system is equal to zero, then the force is said to be balanced force. This doesn't produce any change in the state of the body since the acceleration is equal to zero.
Unbalanced force: If the net force of several forces acting on a system is not equal to zero, then the force is said to be unbalanced force. This produce some change in the state of the body since the acceleration is non-zero.
Relation: When any force is added or removed from a balanced force, then the force becomes unbalanced.