Conditional formatting changes the appearance of a cell range based on conditions (or criteria). If the condition is true, the cell range is formatted based on that condition; if the condition is false, the cell range is not formatted based on that condition. It is easily add conditional formats to your cells; for example, you may want to change the background color of a cell based on the cell's value. You can use a named style to specify various formatting options such as borders and colors to apply if the condition statement is valid. Moreover, visualization such as data bars, color scales, and icon sets can be used with conditional formatting to help you visually answer specific questions about your data, highlight interesting cells or ranges of cells, emphasize unusual values, and visualize data.
Visit the online documentation for more information.
See a sample in action here.