According to Huygen's Principle, each point of the wavefront is the source of :

secondary disturbance

According to Huygen's Principle, 

1. Each point of the wavefront is the source of secondary disturbance and wavelets emanating from these points spread out in all directions with the speed of the wave.
2. A surface touching these secondary wavelets, tangentially in the forward direction at any instant gives the new wavefront at that instant. This is called secondary wavefront.