Here's a breakdown:

* Wavefront: A wavefront represents a surface where all points on the wave have the same phase. Imagine it as a line or a surface that connects points with the same value of the wave (e.g., the crest or trough of a water wave).

* Ray: A ray is a line that represents the direction of energy propagation of the wave. It's perpendicular to the wavefront at any given point.

Think of it like this:

* Imagine a ripple spreading out from a point in a pond. The wavefront is the circle that the ripple makes. The rays are the lines that point outward from the center of the ripple, always perpendicular to the circle.

This relationship between rays and wavefronts is fundamental to understanding wave phenomena like reflection and refraction.