Queue Visualization

Trace operations on an empty queue: Enqueue $3$: queue is $[3]$

Enqueue $7$: queue is $[3, 7]$

Enqueue $1$: queue is $[3, 7, 1]$

Dequeue: returns $3$, queue is $[7, 1]$

Front: returns $7$, queue stays $[7, 1]$

Dequeue: returns $7$, queue is $[1]$

Elements leave in the order $3, 7, 1$, the same order they arrived. That's FIFO.