Curve represents the relationship between Mouse Speed and Cursor Speed on screen,
the default one(straight line) can provide 1:1 mouse movement and cursor movement,
It is suitable for most of the situations.
But it can be changed as you like,no harm will be done to your hardware, just try and feel how your aiming and turning speed are effected by it.
if more detail in need, please let me know,
will provide it if it is not against our NDA.