Mudras are the Yoga of the hands. They are translated as a 'seal' or a 'gesture'. We can activate certain energies at the tip of our fingers by creating a seal between certain fingers of the hands. One of the most beneficial hand positions to learn is the Apana Vayu mudra which gives instant help for first aid to cardiac issues.
Let my dear teacher, Indu Arora, introduce this mudra with and exempt from her book.
Indu Arora: Mudra - the Sacred Secret.
How does this mudra work? Every finger in the body is associated with a certain energy:
Thumb - Fire
Index Finger - Air
Middle Finger - Ether
Ring Finger - Earth