1. Reflection: This is when a wave bounces off a surface. Think of a ball bouncing off a wall, or light reflecting off a mirror. The angle of incidence (the angle the wave hits the surface) is equal to the angle of reflection. This is a fundamental principle in optics and other wave phenomena.

2. Refraction: This is when a wave changes direction as it passes from one medium to another. Think of a straw in a glass of water appearing bent, or light bending as it enters a prism. This happens because the wave travels at different speeds in different mediums.

3. Absorption: This is when a wave's energy is transferred to the matter it encounters. Think of sunlight warming the ground, or a microwave heating food. The matter absorbs the wave's energy and converts it into another form, like heat.