Wave Packet (Wave Group) #
It is a localized wave or undulation that behaves like a single, moving mass of waves.
There is only one point where the amplitude reaches its maximum.
When focusing solely on this wave packet, it appears to behave as if it were a particle. In other words, intuitively, a wave packet can be thought of as a particle.
This explanation is physically somewhat imprecise.
Group Velocity #
The velocity at which the overall shape (the wave packet) propagates when multiple waves are superimposed.
$$v_g = \frac{d\omega}{dk}$$Phase Velocity #
The velocity of each individual wave.
$$v = \frac{\omega}{k}$$