You can press modifier keys (Ctrl, Alt, Shift and Super) together with regular keys like A or S, etc. to produce a unique key combination.
Does anyone know the total number of possible combinations?
Bear in mind Left Shift+A and Right Shift+A could be two different combinations but I'm not sure. I tried googling this question but didn't find an answer.
NOTE: My keyboard has 12 function keys plus a Fn function key modifier key for things like brightness control, media playback control, etc. Some of these key combinations might be tied into ACPI or laptop hardware and don't count. There is also a separate directional control region (Home, PgUp, arrow keys, etc. plus a separate numeric keypad.