couple of ?'s about stock wires an about alternator wire?

[lances]

The previous owner of my truck has tapped in to some kind of power wire that is coming from what I'm calling a junction block on my fire wall so here are the few ?'s I have.
1st. ? What I'm calling a junction black on the fire wall does that come from factory? (left of green circle)
2nd ? If so what is it for?
3rd. ? The 2nd red wire is from the post on the back of the alternator an is tapped into the wires by the fire wall that wire should go directly to the battery correct? (I have the wire circled that's from the back of the alternator)
This is on a 1982 swb gmc w/ a 305