Similar to the buttons on the DualShock 4 attachment that Sony is releasing on January 23rd, the ones on the new design seem to be programmable. You can, say, assign them other buttons' functions to make your game's controls feel more intuitive and easier on the hands.

Polygon says the back buttons may be moved to other places, which could either mean that the controller can be customized or that there might be other iterations of the design. Unfortunately, it's unclear if Sony conjured up the controller for the PS5 and if it will even be released as a real product at all.