Final answer:
The fill handle is a feature in spreadsheet programs used to copy formulas or formatting by dragging the black square located at the bottom right of a selected cell.
Step-by-step explanation:
The fill handle is a little black square in the bottom right corner of the selected cell used to copy formulas or formatting in spreadsheet programs such as Microsoft Excel or Sheets. You can click and drag the fill handle to fill adjacent cells with the same formula, numerical increments, date series, or even copy the same value across a range. Not only does it help speed up data entry, but it also ensures consistency within your data sets.