When a list appears as an element of another list , it is called a nested list .
Example:
list1 = [1,2,'a','c',[6,7,8],4,9]
To access the element of the nested list of list1, we have to specify two indices list1[i][j] . The first index i will take us to the desired nested list and second index j will take us to the desired element in that nested list.
Example: