Factorio Forums

What is this supposed to mean? ... I mean I tired pressing them, but it seems I only used them in wrong context .. so nothing has happened when I done it.

So I still have no clue what they are about

Try pressing them when you're holding stone brick or concrete in your hand.

If you're holding a stack of stone bricks in your hand you can place them on the ground by pressing the left mouse button.
By pressing + or - on the Numpad / Numeric keypad you can increase the area (1x1, 2x2, 3x3, ... tiles) that is affected by this transformation.

So if you have a lot of stone bricks / concrete in your inventory you can easily pave your whole base with roads instead of doing it tile-by-tile.

Was going the "green path" ... and never plastered my base.
I simply ignored concrete and stones (aside from furnaces).
That's really useful thanks