Spreadsheet feature that allows automatically adding color, text styles, etc. to certain cells or ranges of cells based on the data workbook
Conditional formatting is useful to automatically format large ranges of cells, particularly based on the value of the cell or its neighbors. For example, you could automatically format cells with a negative value as red.
Conditional formatting can also let you color-code cells based on (for example) how close they are to the average value of all cells, or their relationship with other cells.
Another use well suited for conditional formatting is to set a cell's background and text color to white based on some criteria, thus hiding the data (for example, hiding cells on a bank ledger sheet if they are the same as the last date's value).
In both Microsoft Excel and LibreOffice Calc, conditional formatting is activated by going to
Format > Conditional Formatting
on the main menu bar.