Why is accessing an item by index slower in a linked list than an array?

I think I am missing a very obvious point but could not find it in my Java textbook.

I understand that node storage does not necessarily have to be contiguous in memory for linked list. Does this also mean that a linked list is not indexable? If so, then the only way to find an item in a linked list is to traverse the list, right, whereas you can get from an array by index?