KwCheng's blog

In C++, an iterator is any object that, pointing to some element in a range of elements (such as an array or a container),

 has the ability to iterate through the elements of that range using a set of operators

 (at least, the increment (++) and dereference (*) operators).

The most obvious form of iterator is a pointer: A pointer can point to elements in an array,

 and can iterate through them using the increment operator (++). 

But other forms of iterators exist. For example, each container type (such as a vector) has a specific iterator type designed to iterate 

through its elements in an efficient way.

ref : http://www.cplusplus.com/reference/std/iterator/