Excel provides us with many options that make it easier and fasters to enter data and edit data. One of these options is auto-fill. The auto-fill option allows you to complete a series automatically by just dragging cells. You can use auto-fill to complete series like numbers, days, months, years, and so on. To use auto cells for filling a number series, just type the first two numbers in the first two cells, select both the cells, and drag the cursor to the required number of cells and excel will automatically fill in the series. The same can be done for days or months. Auto-fill also allows you to copy the same data into multiple cells. Just type the data in one cell and drag the cursor and the data is copied into the adjacent cells. Auto-fill also allows you to fill data relative to the completed row or column next to the required cells. If you have data from cell 1 to 25 in column A, then you can just type the first entity of the required content in B1 and double click on the cell. Excel will automatically fill in the series until B25.