Mudras are described in detail in ancient yogic texts and scriptures, such as the Gheranda Samhita, Hatha Yoga Pradipika, and Shiva Samhita.
According to Ayurvedic medicine, our hands hold the endpoints of energetic pathways carrying prana (life force energy) through our body. These energy pathways are called meridians (the same meridians used in acupuncture and reflexology).
Mudras allow us to go inward and recharge our energy flow through our chakras, and also our physical body.
The term applies to the use of specific hand gestures during meditation, yoga and or mantra, that carry specific goals of channeling your body's energy flow.
There are more than 100 known mudras that have been developed over the centuries.