what is the difference between a load line and a characterstics curve, because both are the plot between Vce and Ic (for a common emitter ) .

 

What datasheet are you refering to (that is assuming that you are)?

 

what is the difference between a load line and a characterstics curve, because both are the plot between Vce and Ic (for a common emitter ) .

A load line is unique to the load resistor in a given circuit. The characteristic curves are properties of the transistor independent of the values of any external comnponents. In the characteristic curves, the base current is a parameter which is held constant on each curve.