AutoCalculate

When two or more cells are selected and at least one of them contains a numerical value then the sum of the values is automatically displayed in the status bar.
This allows you to obtain a temporary result from a function without having to actually use a formula.
This can be very useful to make quick calculations without them appearing on the worksheet.

The section of the status bar that is used to display the result is in the bottom right corner.

AutoCalculate Shortcut menu

You can use the Right mouse button to click anywhere on the status bar to display a shortcut menu.
Just select the relevant function to display its result in the status bar.

None - Turns the AutoCalculate feature off.
Average - Calculates the average number in the range of cells.
Count - Total number of non blank cells.
Count Nums - Total number of cells that contain numbers.
Max - Calculates the largest number in the range of cells.
Min - Calculates the smallest number in the range of cells.
Sum - Calculates the total of all the numbers. This is the default.

Important

It is possible to hide the status bar completely by selecting (View > Status Bar). This is a toggle.