This traversal mechanism is quite complex since there is different schools of thought for the design and implementation of such pattern and hence deserves a chapter of its own in this documentation. Some containers such as priority queues or binary search trees keep their items sorted. On the other hand some other containers do not necessarily keep their items sorted but provide facilities to sort them on demand according to various comparison criteria and sorting algorithms. As just said, this facility depends on various criteria such as sorting algorithms and here again deserves a chapter of its own in this documentation. Have a look at the flat-short form for a complete list of these features.
Some containers allocate chunks of memory to hold their items.