Which data structure operates on a First In, First Out (FIFO) principle?

The data structure that operates on a First In, First Out (FIFO) principle is a queue. In a queue, the first element added to the structure will be the first one to be removed, resembling how items might be processed in real-life scenarios such as a line of people waiting for service.

When an element is added to the queue (enqueue), it is placed at the back, and when an element is removed (dequeue), it is taken from the front. This orderly processing ensures that items are handled in the order they arrive, making queues particularly useful in scenarios like scheduling tasks, buffering data streams, or managing requests in a system where order matters.

In contrast, other data structures mentioned, like stacks, operate on a Last In, First Out (LIFO) principle, where the last item added is the first one to be removed. Trees and graphs are designed for different kinds of relationships and traversal, not based on the orderly queuing of elements like a queue.