This is a wonderful question! This is a spectral waterfall display of audio frequencies. The dense area on the left are the CW (Morse code) portions of the spectrum where there are quite a lot of people communicating in Morse code. The bright bands just to its right is the FT8 data mode (which also uses audio frequencies) to send and receive very short messages. The broad area on the right are people communicating via voice transmissions on Single Sideband.
This is a wonderful question! This is a spectral waterfall display of audio frequencies. The dense area on the left are the CW (Morse code) portions of the spectrum where there are quite a lot of people communicating in Morse code. The bright bands just to its right is the FT8 data mode (which also uses audio frequencies) to send and receive very short messages. The broad area on the right are people communicating via voice transmissions on Single Sideband.