What are mudras in Yoga?

Mudra is a term with many meanings. It is used to signify a gesture, a mystic position of the hands, a seal, or even a symbol. However, there are eye positions, body postures, and breathing techniques that are called mudras. These symbolic finger, eye, and body postures can vividly depict certain states or processes of consciousness.

Conversely, specific positions can also lead to the states of consciousness
that they symbolize. What does this mean in concrete terms?
For example, a person who frequently and fervently does the gesture of
fearlessness, which can often be seen in the depiction of Indian deities, will
also be freed from fearfulness with time. So mudras engage certain areas
of the brain and/or soul and exercise a corresponding influence on them.
However, mudras are also effective on the physical level. I discuss this in
the section called "Mudras and Other Hand Therapies."
We can effectively engage and influence our body and our mind by
bending, crossing, extending, or touching the fingers with other fingers.
Isn't this wonderful?
In Hatha Yoga,1 there are 25 mudras. These also include eye and
body positions (asanas) and locks (bandhas). In this book, I will only briefly
touch on them and mainly describe the hand mudras. Especially in Kundalini Yoga,2 the hand mudras are used during the body postures to
intensify their effect. The kundalini expert Lothar-Riidiger Liitge
explains: "In this respect, Kundalini Yoga assumes that every area of the
hand forms a reflex zone for an associated part of the body and the brain.
In this way, we can consider the hands to be a mirror for our body and our
mind."

As I recently meditated on the term mudra, I became particularly
aware of the symbol of a lock. A lock always conceals a secret. We frequently
use gestures in an unconscious way to seal something; for example,
when giving special weight to a decision, or reaching an agreement with
another person, or even with cosmic consciousness. In precisely the same
way, we may also seal something with our inner forces—we reach an understanding
with ourselves. I don't believe we will ever completely understand
the essence of the mudras. The enigmatic touches on the Divine—so each
mudra ultimately creates a special connection to cosmic consciousness (or
however you prefer to call the Divine). This symbolism, in particular, is the
basis of the best-known hand mudra of yoga, the Chin Mudra.
The thumb is symbolic of cosmic (divine) and the index finger is symbolic of individual (human) consciousness. The ultimate or primary goal of yoga is the oneness of humanity with cosmic consciousness. With this gesture, the human being expresses this desire, this longing. It is interesting to note that both these fingers belong to the metal element in
Chinese Five Element Theory (see Appendix C for more about this topic).
Metal is the material that is the best conductor—it conducts energy.
According to this teaching, the metal element also creates the connection
with the cosmic world, and inspiration and intuition dwell in this element.
The index finger represents inspiration (energy from the outside) and the
thumb stands for intuition (inner energy). In this gesture, intuition and
inspiration form a closed unity. The power of the microcosm and the
macrocosm are connected and mutually fructify each other. We see that if
we dig into the depths of the ancient teachings long enough—or go far
enough into the heights—we will find ourselves at the other end again.