'combo' challenge - please explain to me how for...in... statement works.

# combo([1, 2, 3], 'abc')
# Output:
# [(1, 'a'), (2, 'b'), (3, 'c')]

#Correct Answer:
def combo(it1, it2):
    final = []
    count = 0
    for i in it1:
    # <OR this also works:> for i in it2:
        component = (it1[int(count)],it2[int(count)])
        count += 1
        final.append(component)
    return final

#But why doesn't the one below work? This one makes more sense to me
#because you are iterating through both items in the 'combo' function, right?
#I may be misunderstanding something here so I would appreciate if someone can enlighten me!
def combo(it1, it2):
    final = []
    count = 0
    for i in it1,it2:
        component = (it1[int(count)],it2[int(count)])
        count += 1
        final.append(component)
    return final