What is a stack and why is it important in Linux or Computer Science, for that matter? A stack, in the context of this article, refers to a last-in-first-out (LIFO) list or more affectionately referred to as a pushdown store. This is in contrast to another arrangement called first-in-first-out (FIFO) used in granaries since the grain is loaded at the top of the tower and dispensed at the bottom into trucks or other vehicles for delivery to its destination.