What is an index?

what really confuses me is : “for index in range(len(lst1)):
if lst1[index] == lst2[index]:” so in the first line “index” represents that it would iterate through every element in lst1, that’s fine. But how can it iterate through the lst2 when there was no distinct declaration like: “for i in the range(len(lst2)):” sometimes you need to have two variables called for 2 lists, for example the exponent challenge exercise, we had to call 2 variables to work that out, but in this case my code:
def same_values(lst1,lst2):
indice_lst=[0]
for i in range(0,(len(lst1))):
for j in range(0,(len(lst2))):
if lst1[i]==lst2[j]:
indice_lst.append(i)
didnt work because i didn’t call for the same variable. now i’m confused how to understand this iteration behavior of python. can anyone kindly tell me what’s it, that i’m doing wrong???