The maximum distance that particles of a medium move from their rest position is called the amplitude of the wave.

Here's a breakdown:

* Wave: A disturbance that travels through a medium, transferring energy without transferring matter.

* Medium: The substance through which a wave travels (like air, water, or a solid).

* Rest Position: The equilibrium position of a particle in the medium before the wave passes through.

* Amplitude: The maximum displacement of a particle from its rest position as the wave passes.

Think of a wave on a rope. The rope particles move up and down, and the amplitude is how far they move from their flat, resting position.