The Anatomy of an Audacity Track

Let's talk about the anatomy of a track in Audacity. What's all the stuff in the track header and what do we need to know about it? How do I change the scale and what do the sliders in the track header do? How do the settings in the track header affect my exported audio?

[highanddryful]

Mike thank you this has been a very informative tutorial. Can you tell me why the envelope tool does not respond when I click it? How do I activate the tool please?

[taab]

Mike, I don't understand the relationship of the linear scale to the level bar? You say that your audio was recorded at -19 lufs, so what specifically is the linear scale representative of? What aspect of the waveform is +1 to -1 representative of? Your audio was peaking at 0.70 on the linear scale. 0.70 of...what?
What specifically is being indicated or measured at 0.70 in relation to the -19 lufs? The level bar clips at zero db's - so what is 0.7 representative of?
Secondly, I've heard it said (erroneously perhaps, ) that the bottom half of the waveform is a mirror image of the top half, but the bottom half is often different looking to the top half - so why is there a difference in appearance?

[highanddryful]

Mike thank you this has been a very informative tutorial. Can you tell me why the envelope tool does not respond when I click it? How do I activate the tool please?