Queue
In plain terms
A first-in, first-out collection where items leave in the order they arrived.
Going deeper
You add to the back (enqueue) and remove from the front (dequeue). Queues model fair, ordered processing and are everywhere: task scheduling, message buffers, and breadth-first search.
Under the hood
Backs BFS, scheduling, and producer-consumer pipelines; variants include circular buffers, priority queues, and double-ended deques. Distributed versions add durability.
Examples
Print job queues, task queues (Celery), message brokers (RabbitMQ, SQS), BFS frontier.
Think of it like...
Like a line at a coffee shop: whoever got there first is served first, and newcomers join the back.