The axis going up is amplitude, the one going right and down is time, and the new axis rightward and upward (left to right on the right-hand chart) is frequency.
The left chart doesn’t show the frequency axis. The right one doesn’t show time.
The wave shown on the left in the dark cyan color is (shown to be) composed of two different waves of two frequencies shown on the left in gray and in the space between charts as dark cyan. The higher frequency one is lower amplitude.
The axis going up is amplitude, the one going right and down is time, and the new axis rightward and upward (left to right on the right-hand chart) is frequency.
The left chart doesn’t show the frequency axis. The right one doesn’t show time.
The wave shown on the left in the dark cyan color is (shown to be) composed of two different waves of two frequencies shown on the left in gray and in the space between charts as dark cyan. The higher frequency one is lower amplitude.