random_item why end with [] when no list was created?

Ok so i managed to pass this test through the help of the forum, but i am here to learn.

So in this exercise we created a function named random_item. All good so far. Then we've thrown iterable into this mix. Did i miss when this was discussed? I had to google it. I think i understand it correctly.

iterable is an object able to returns its members one at a time is that correct?

So we've done that in the first line.

Then creating what looks like the iterable sum ?

then the return. What really threw me was the [] did we turn treehouse into a sort of list? Is that why we use [minus] ? This task really threw me off.

Sorry if this seems really stupid, but i just want to know why we do this. It's hard for me to do something without knowing why it is done.

Thanks,

# EXAMPLE
# random_item("Treehouse")
# The randomly selected number is 4.
# The return value would be "h"
import random

def random_item(treehouse):
    minus = random.randint(0, len(treehouse)-1)
    return treehouse[minus]