#1
Alright so I've been realizing that many guitarists around me use I think alternative picking? Well it is when you, I guess double pick in one string to play faster, and not tremolo. I down pick always as a regular, and of course alternative picking if I'm gonna do a breakdown or w/e, but I mainly down pick. What's the difference?
#2
Alternate picking is just switching between down and up picking.

for example, if you need to hit the same note twice in a row, instead of down picking twice (down, down) you go 'down, up'