CALC : What are the buttons at the left of the Column header?

[TaoRich]

Hi folks,

In LibreOffice Calc:

What are the two buttons on the top left of the Column header.
[1][2]

I have searched for an answer, but am not able to find one.

Thanks
Rich

[TaoRich]

Thanks JohnSUN … I looked up grouping in the Help and learnt something new.

[handydoug]

Thanks JohnSUN. It solved a mystery for me.

[JohnSUN]

Do you mean this numbers?

This is a Group - very handy tool for hiding unnecessary data