phase velocity, group velocity

group velocity: overall shape of the wave's amplitudes — known as the modulation or envelope of the wave — propagates through space.

The group velocity is often thought of as the velocity at which energy or information is conveyed along a wave. In most cases this is accurate, and the group velocity can be thought of as the signal velocity of the waveform.

phase velocity: This is the speed at which the phase of any one frequency component of the wave travels. For such a component, any given phase of the wave (for example, the crest) will appear to travel at the phase velocity.