Map is a Sorted Associative Container that associates objects of type Key with objects of type Data. Map is a Pair Associative Container, meaning that its value type is pair. It is also a Unique Associative Container, meaning that no two elements have the same key.

Map has the important property that inserting a new element into a map does not invalidate iterators that point to existing elements. Erasing an element from a map also does not invalidate any iterators, except, of course, for iterators that actually point to the element that is being erased.