It often happens that you create a formula where you also need to copy that formula into many cells below it in the same column.
The standard way most people will do this is to drag from the lower right-hand corner, or possibly even right click and copy the formula, which will work but is really not very efficient.
If you decide to drag it down all the rows in the column it can become a very time-consuming exercise, especially if you have a spreadsheet with thousands of rows.
The fastest way will be to double click the lower right-hand corner instead of starting to drag it. This will immediately copy the formula, text or value down the column until the first completely empty row.
To view the range, it was copied to you can press Ctrl + period (.) and then press it again. This will move the active cell between the first and last row of a highlighted range.