Basic question- for _ in range(#)- What exactly causes the loop?

[Ignis]

I am really wanting to dissect things so I know why things occur, rather than they just do. The example in my text book says "for i in range", but the same results occur if I use "for x in range" or "for z in range"

Can anyone explain what exactly causes the loop, and what the variable is doing?

[andrean]

range creates a list of numbers actually, so range(10) will be [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

for i in range(10):

causes i to step through that list, at each step i gets it's value from the list.