Here is one simple real-time working example where a Queue class can be used.

When you walk into a bank or a passport office, you will collect a token and wait in the queue for your token number to be called.

From the application perspective, when a token is issued, the token number will be added to the end of the Queue.

When a representative at the counter is available to server a customer, he will push the "Next" button and the token number that is present at the beginning of the queue, will be dequeued. So, this is one example, where a Queue collection class can be effectively used.