Radio waves can propagate from transmitter to receiver in four ways: through ground waves, sky waves, free space waves, and open field waves.
Ground waves exist only for vertical polarization, produced by vertical antennas, when the transmitting and receiving antennas are close to the surface of the earth.
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere.
The term wave propagation refers to the movement of waves.
All waves have frequency, amplitude, wavelength, and wave speed.
Wave propagation speed quantifies how fast the wave travels.