Conditional Formatting is used to highlight interesting cells or ranges of cells, and visualize data by changing the appearance of cells based on specified conditions. There are many built-in conditions and you can also create your own conditions by using formulas.
This video shows conditional formatting of a cell/range of cells based on the contents of another cell using formulas. This has got varied applications limited by your imagination only. 🙂
All in all, helping you Excel @ Work!