what is this code mean?

Question

list = [1，1，2，3，5，8，13]
print（list [list [4]]）

I don't know the line 2, nesting of two list

Answer 1

It means take the list item indexed 4 (the number 5) and use it as an index indicator.
list[4] == 5, so:
list[list[4]] == list[5] == 8