Reflection - the bouncing back of a particle or wave that strike a boundary between two media.The angle of incidence equals the angle of reflection (both measured with respect to the normal represented by a ruler in this video).
Refraction - the change in direction of a wave as it crosses the boundary between two media in which the wave travels at different speeds. The yellow area is shallower and therefore the waves travel slower there. This causes the waves to bend toward the normal.
Diffraction - the bending of a wave around a barrier, such as an obstacle or the edges of an opening. In this case, diffraction occurs when the size of the opening is about the size of the wavelength of the waves.
Interference Pattern - A pattern formed by the overlapping of two or more waves that arrive in a region at the same time. Where crests meet with crests or troughs meet with troughs (the bumpy lines) constructive interference occurs. These are called lines of antinodes. Where crests meet troughs (the smooth lines in between the bumpy lines) destructive interference occurs. These are called lines of nodes.