What does ++ have to do with C++ iterators?

  int i = 0;
  i++;

How could that possibly involve an iterator? Moreover, C doesn't even have iterators.

You can use ++ on an iterator. Indeed you often do, e.g. in loops. ++iterator is preferable, and for consistency/so you don't have to think about its often recommended in C++ environments to just generally use pre-increment.

(Copying an iterator might be a lot more expensive than just copying an int, and might not be effectively optimized out by the compiler - e.g. if someone builds an iterator that's referenced-counted to an owning object or something)