What is the difference between accessing vector elements using an iterator vs an index?

Question

What advantages are there in accessing vector elements using an iterator vs an index?

Answer 1

Modularity is the answer. Suppose you wrap your logic in a function call (a good practice). In that case making it receive iterator will make it generic, so that it can operate on a C style array (pointer), an C++ stl vector or anything really that behaves like an iterator container, such as a linked list for instance.