45: Collections: Iterators Part 1.

Iterators give you the ability to navigate from one item to another in a collection. Why is this so special? Now that you know how to work with various collections, you know that they are structured very differently. An array just needs to move a pointer to the next item. A list needs to follow wherever the next pointer leads. A binary tree needs to go up and down the tree. Iterators give you a common way to navigate no matter what kind of collection you are using.