What is a priority queue and how does it differ from a regular queue?

A priority queue is an abstract data type where each element has a priority, and elements with higher priority are served before elements with lower priority regardless of their insertion order. Unlike regular queues (FIFO), priority queues process based on priority. They are typically implemented using heaps for O(log n) insertion and O(1) peek of highest priority. Common uses include task scheduling, Dijkstra's algorithm, and event-driven simulation.