The Queue is a FIFO (first-in, first-out) data structure. It means that any data stored first will be the first to be removed - just like a queue.
The person first in a queue is the one who gets out of the queue first!
enqueue: attaches an item to the end of the queue
dequeue: detaches the first item from the queue
first: returns the first item of the queue without removal, just like peeking in the Stack data structure