In Calc, what does block selection mode do?

There are 4 selection modes in Calc: standard, extended, adding and block. I assume that the logic is the same as for selection mode in Writer. However, I am not clear what block selection does. How is it different from standard selection mode?

Also, while all of the selection modes presumably apply to cells, it appears that only standard selection mode applies to text. Is that correct?

There is no block selection mode implemented in Calc (the standard selection mode is always block). Hence the request in tdf#122280 to remove that item from the dialog.

Standard selection Click in text where you want to position the cursor; click in a cell to make it the active cell. Any other selection is then deselected.

Extending selection (F8) Clicking in the text extends or crops the current selection.

Adding selection (Shift+F8) A new selection is added to an existing selection. The result is a multiple selection.

Block selection (Ctrl+Shift+F8) A block of text can be selected.

That is what the documentation says but I want to know what it means. What does block selection do that is different from what standard selection does?

Can anyone answer my questions?