One of the most common (if not the most common) of all hand gestures in yoga is the Seal of Consciousness a.k.a. Chin/Jnana Mudra. Whereas chin translates to consciousness, mudra meaning seal or gesture and jnana is known as wisdom.
The hand gesture is symbolic when connecting the thumb and index finger of either or both hands. The index finger represents the individual consciousness and the thumb representing universal consciousness to which the word yoga translates as the unification of both cosmically.
The other three fingers also represent a gesture towards purification from impurities of ego (middle) and the dissolving of karma (ring) and illusion (little).
These two versions of the same hand gesture derived from Hath yoga shows the upright palm facing Jnana mudra (passive receiving) and palm down facing chin mudra (actively giving). The hands could be placed on the knees while in a seated position or having one hand in front of the chest drawn inwards. These locations where the hands are is vital as they stimulate energetic lines within the body called nadis activating a pranic circuit or pathway within the body.
Not only does this mudra help in maintaining a constant state of internalizing our focus but also directing all our energies into alignment towards Samadhi.
Experience this mudra in your yoga space which includes meditation and set a solid foundation for your practice to build upon.