Everyone is fond of shortcut but feels who will learn all shortcuts and every company uses different controls according to their options. So it is impossible to remember every shortcut.
But on other hand if you learn few keys and understand their roles it will reduce working time and also learning time of shortcuts.
Control Key- Originally it doesn’t do anything, but in combination it can do alot. As every major shortcuts have Control key and in addition other keys.
Shift- This keys is used rarely in shortcuts but this key lets you perform small caps to large caps. And second major role is to shift from basic qwerty keyboard to symbols or special characters (such as @, #, ₹, &, *, etc).
Alt- This is the main key on keyboard if you press alt in Microsoft it shows up all the shortcut on screen to that perticular software. Or in combination it gives more ways of alterations.
Tab- It is used to create space much bigger than space bar. But in combination you can move in screens as Alt+Tab.