What is the difference between exponential factor and orientation factor in case of Arrhenius equation?
The orientation factor is really an empirical add-on fix as way of trying to make the Arrhenius equation seem more reasonable. Most collisions between molecules do not lead to reaction, which is why the activation energy is there, but even when a molecule has obtained enough energy to react ( by random collisions in solution or vapour)  we may know from its structure that it can only react from one side or at one end, then an orientation factor is added.