I use them a lot. It’s basically a “quick” way to access various features. For example, with just a press of the z key and a move to the upper right, you can go into rendered view mode or by pulling down with the mouse, you can go to solid shading mode. Or after you press the Z key, you can wait and see which view mode you want to be in. Same thing with the tab key and switching between Edit, Sculpt, Object, etc. There are others, but these are the two I use the most.
