Huygens Principle states that every point on a wavefront can be considered a source of secondary wavelets. These wavelets spread out in all directions at the same speed as the original wave. The new wavefront is formed by the envelope of these secondary wavelets, illustrating how waves propagate through space. This principle helps explain various phenomena in wave behavior, such as diffraction and interference. It is fundamental in understanding how waves, including light and sound, travel and interact with obstacles, leading to important applications in fields like optics and acoustics.