A PriorityQueue is a list that always keeps its items sorted based on some rule, like smallest to largest. So, when you take an item out, you always get the one with the highest (or lowest) priority.

To remove an item from a queue, use the POPN, POPC, POPL, or POPO function. As with stacks, you should use the ITEMTYPE and LISTLEN functions to verify the item's type and the list's length before ...

The ConcurrentStack and ConcurrentQueue classes, lock-free and thread-safe implementations of the Stack and Queue classes, build thread safe collections in .Net ...

Matt Wallaert says there are technical reasons why stack ranking is a flawed system. He argues that even if all the technical issues were fixed, it would still be a damaging review system.