A queue is a waiting line. You add items at the back and remove them from the front. Nobody jumps ahead, so the order you arrive is the order you leave.
FIFO means first in, first out. The item that waited longest gets served next. A ticket counter works this way. The person at the front, who came earliest, is called first.
This fairness makes queues natural for scheduling and buffering. Print jobs, task runners, and message pipelines process work in arrival order. When order and fairness matter more than recency, a queue fits. It keeps the oldest waiting item from starving behind newer arrivals.
Rewriting in plainer words…
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A queue is a waiting line where items join at the back and leave from the front, and nobody jumps ahead.
FIFO means first in, first out, so the item that has waited longest is always served next, like the earliest person at a ticket counter.
That fairness makes queues a good fit for scheduling and buffering, so print jobs, task runners and message pipelines all handle work in arrival order.
I'd pick a queue when order and fairness matter more than recency, because the oldest waiting item can't starve behind newer arrivals.
If the newest item should go first, like undoing the last action, a stack fits better, and if some jobs are more urgent than others, a priority queue does.
Weak answers to avoid
Just expands the acronymSaying 'first in, first out' proves nothing. Say which end you add to, which end you remove from, and that the longest-waiting item goes next.
Removes from the same end it adds toThat is a stack, which is LIFO. A queue adds at the back and removes at the front, so the oldest item leaves first.
Defines it but never says when to use itInterviewers want the why. Tie FIFO to fairness and arrival order, name a real use like print jobs, and say when recency matters more and a stack fits.
Calls a priority queue just a queueA priority queue serves by priority, not arrival order, so it breaks FIFO. Mixing them up suggests FIFO is a memorized phrase, not an understood rule.
Interview lens
Likely follow-ups, what you can say, and the weak answers to avoid.
