[joerich]

My attempt to try to help you:

1st picture: you see a red signal and “f” which means that the signal is in the “time world”. The x axis represents the time.

2nd picture: The “f” disappears and a lot of signals in blue color appear. If you add up all these blue signals the result is the red signal. As you can see there are a lot of different blue signals with different frequencies.

3rd picture: they do that 3D breakdown where you can see each signal and on the right appears another graph/plot which represents the Fourier Transform. This graph/plot is in the “frequency world” and the x axis represents frequency. Each frequency of each blue signal is represented as a straight line. This line is a only blue signal located in its frequency and the more larger is in the y axis the more representative is in the final result (which is the red signal). The largest straight line is the one on the left because is the one with more energy in the “time world” and for that is the more representative in the frequency plot. The f with that arch is the Fourier Transform.

4th picture: they show you the signal on the “time world” and the signal in the “frequency world”.