Junction Block Explained...Plz!!!!

[love my 72]

After a few hours using the search function of the site I'm yet to find a clear explanation of the purpose of the junction block an the wires that go to it. You know the diamond shaped plastic thing-a-mo-bober on the fire wall.

I spent the better part of an hour earlier today holding the wire harness from an 86, V8 Gas truck in my hand and a good half hour on the wire diagram found here: http://www.73-87chevytrucks.com/tech..._V8_engine.jpg

seams to me like it one big power loop, can some one please explain/elaborate/confirm the following to me:

1a)Post A of the block has a wire that goes to the bolt that sticks out of the alternator. I'm assuming power flows from the alternator to the junction block?

1b)Spliced in to that wire is a wire that goes back to the fuse block, Im assuming this brings power to the fuse block while the alternator is turning?

2a)Post B of the junction block has a wire that goes to + post of the starter were the battery cable goes, I'm assuming that it brings power to the battery to keep it charged?

2b)There are two other wires spliced in to that + post of the starter. ONE goes back to the fuse block, Is that how the "ACC" setting on the ignition switch powers stuff like radio, power windows, etcetera?

and the SECOND one goes to a plug on the alternator next to the brown wire that i understand is a signal wire for the Amp meter in the dash.