C++ How to Program, 10/e

... at a time. Output iterators support only one-pass algorithms—the same output iterator cannot be used to pass through a sequence twice.
forward	Combines the capabilities of input and output iterators and retains their position in the container (as state information). Such iterators can be used to pass through a sequence more than once (for so-called multipass algorithms).
bidirectional	Combines the capabilities of a forward iterator with the ability to move in the backward direction (i.e., from the end of the container toward the beginning). Bidirectional iterators support multipass algorithms, such as reversing the elements of a container.
random access	Combines the capabilities of a bidirectional iterator with the ability to directly access ...