In Indian philosophy, your body is viewed as being made up of five elements, with each of your five fingers representing one element:
Thumb: fire, sun, radiant matter, heat, light – the energy that drives all other matter
Index finger: air, wind, matter in gaseous form
Middle finger: sky, space, akasha, ether
Little finger: water, matter in liquid form
Mudras consist in using your thumb (fire) tolightly stimulate one or more of the other elements by touching its finger tip, knuckle or base.