In Dr. Hermann Weyl's book 'symmetry', he explains the difference between left and right as
In space the distinction of left and right concerns the orientation of a screw. If you speak of turning left you mean that the sense in which you turn combined with the upward direction from foot to head of your body forms a left screw.
What is meant by that?
Try staring hard at this picture.
It should be clear that, to drive this screw into a block of wood, it has to be rotated clockwise from the top.
This is a "right screw", and the orientation of this screw is different from that of a "left screw", which has to be rotated anticlockwise.