A priority queue is essentially a list of items, each associated with a priority. In general, different items may have different priorities and we speak of one item having a higher priority than another. Given such a list, we can determine which is the highest (or the lowest) priority item in the list. Items are inserted into a priority queue in any arbitrary order. However, items are withdrawn from a priority queue in order of their priorities starting with the highest priority item first.

The key topics for this lesson are:

1. Priority Queues
2. Heaps
3. Heap Deletion and Insertion
4. Storage of Complete Trees
5. The PriorityQueue Class