Adobe mixer question with sends and buss (pics inside)

[BLP]

In figure 1 where I circled, there is up and down arrows at the end. As you click down arrow the send goes from S1 to S2 to S3 etc. What exactly does that mean and do? Then beside it there is a button to click that says Send 1 Pre-Fader-Post Fader. When it's blue it is on. What is this for?

In figure 2 when we switch from the mixer to the "main tab" there is a send level. You see the default setting? What is the term for that? What is this for? What happens as you change setting? The first number it comes to when I move it up is -184. all the way to 15. What happens when it is at 0?


There is send levels on channels and send levels on busses. Do they do the same thing on busses as they do on channels?

 

[Runaway]

Here is how you can use sends for headphone mixes

Set a bus (alt-B) and allocate that to a hardware output
Select S1 and allocate that top the bus that has just been created
Turn that 'volume' knob up to zero

Do the same for any other channels that you want to send to that same bus

You can do the same except instead of a hardware output as in a HP send you could have an fx on the bus and send that bus to the main mix

All sorts of things you can do with sends & busses

Edit: You can set up a 2nd headphone send by repeating all this but this time select S2 and allocate it to the new bus/headphone send
Now you can send the same channel to 2 different sends/outputs and have control over the levels to each send