If stacks process the most recent element first, queues process the oldest one. That single difference — first in, first out — makes queues the backbone of BFS, task scheduling, and anything that needs to respect arrival order. This post breaks down what queues are, how they work under the hood, and why using the wrong implementation can silently destroy your performance.
What is a queue?
A queue is a collection where the first element added is the first one removed. This is called FIFO — First In, First Out.