What is the importance of the 'refractory period' after an action potential has been generated?

The refractory period is a period of recovery after an action potential where the ion channels will not open and the membrane can't be excited or depolarised. This happens to encourage the diffusion of sodium one way along the neurone in order to depolarise the next region. Therefore the refractory period not only makes the action potential unidirectional but also ensures discrete impulses.