FIFO (First In, First Out) is an abstraction in ways of organizing of data relative to time.
Queues are usually despised, being considered a waste of time, either when waiting in front of a cinema for a movie show, or when in a bank to withdraw a check.
The kind of queue we will talk about here is not a waste of time, on the contrary it will save you a lot of time (and some headache) in certain kind of applications.