Map Absolute Raw Input = ignore all programs with mouse acceleration (Windows settings, your mouse software, etc.). If you don't understand what mouse acceleration is, it basically enables a correlation between your cursor speed and cursor sensitivity. The faster you move your mouse, the higher your sensitivity becomes. Your choice to keep it off, but most people will recommend that you have this on.
Confine Mouse Cursor = you can't move your cursor outside of the screen during gameplay. Only applies if you use native resolution/fullscreen mode. If this is off, you will be able to move your cursor in and out of the osu! window at any given point in gameplay. This option does not effect how your cursor moves across the osu! window.