The Level Meter is a very common and recognizable way to measure audio. It displays the output volume of the audio stream. The meter markings are in decibels and are very accurate. The Level Meter offers different ballistics (rise and fall times) settings that are equally accurate. To modify options for the Level Meter, Control/right-click on the meter to invoke a contextual menu containing all available display options.
The Stereograph displays the amount of stereo information in an audio stream. The splayed lines show the general tendency of the output (right or left) or out-of-phase (extreme right or left).
The sliding indicator at the bottom is a phase correlation meter. When the audio stream is mono, the indicator is at +1. When the audio stream is stereo (on average) the indicator tends toward 0. When the audio stream is out-of-phase between channels the indicator tends toward -1.
The Spectrograph will display a signal similar to a frequency graph or fast Fourier transform, commonly known FFT. It renders the spectrum with significantly better detail for music and audio.
The bars can be set for 1/3, 1/6, or 1/12 octave settings. At 1/12 octave setting, each bar essentially represents a musical pitch. This allows for better detail in the low and high frequency ranges and will make it easier to closer to what our ears hear.
There are many options available for the Spectrograph that allow you to precisely set how your audio is measured, interpreted and displayed, including settings for different ballistics, i.e. rise and fall time response, that are all equally precise.
To explore these settings, open the Spectrograph contextual menu with a control-click or right-click directly in the metering window.