What is it?
A queue is very similar to Stacks. They are abstract data structures, meaning while they are not structures themselves, they are ways of managing other linear data structures, like Arrays and Linked Lists.
To characterize a queue structure, one must only retrieve the last elements, and only insert at the beginning of the queue.
The FIFO principle
Queues work with the FIFO principle, which stands for First in, First Out. Much like a queue in real life, the first elements to arrive, are retrieved first, and all others must wait for their turn.