A relative reference is one that automatically updates when it is moved (or copied) within a spreadsheet. If you’re always writing formulas that require certain cell references to be absolute and others to be relative, then you’ll want to be using this shortcut key. Using F4 to Cycle Between Absolute and Relative:

When you’re in Excel (or Word for that matter) and you’ve just completed a task, maybe formatting a cell, deleting/inserting a row, or anything that’s repetitive simply push F4 the next time you need to complete that task.

The one people seem to like the most is the repeat functionality, and really this is where the time savings will come into play once you get used to using F4. The F4 function is used for one of two tasks: 1) Cycle between absolute and relative references (in a formula) and 2) Repeat the last action.