LIFO stands for "Last-In, First-Out". It refers to a data structure called a stack, which operates based on the LIFO principle.
In a stack, items are added to and removed from the top of the stack. The last item added to the stack is the first one to be removed, and the first item added is the last one to be removed. This is similar to a stack of plates, where the most recently placed plate is the first one to be removed, and the bottom plate is the last one to be removed.