The art of Indian Dance (traditional) is a amalgamation of facial expressions, body postures and hand gestures. All three must be used in unison to express a feeling / event / scene.
Most Indian dance routines have a context and a back story.
These Mudras (Hand gestures), have specific meanings in the context. So if you are aware of the context, the back story and various aspects of the dance, its easy to become immersed into the act. Its like a mime play.
As an example, the last mudra, the one with the three fingers, represents the weapon of Lord Shiva, with which he uses to kill sinners.
At 58:25, there's english explanation along with mudras. I hope that gives you some idea.
This is how it looks in Mohiniyattam, a different form -- https://www.facebook.com/shaaledotcom/videos/502594377555050 . The dancer depicts a scene where Indra (a god) comes to visit the wife of a sage. He comes in the disguise of the sage (when the actual sage is away) and the wife sees through that and laughs at him.
Mudras connect meridians together to rechannel how bioelectric energy (chi/prana) flows through your body. It's like connecting wires on a circuit board, and only has any real effect if you actually have a reasonable amount of chi flowing round your body.
Mudras are supposed to have some kind of effect on your mind (although I haven't experienced much of that), but I've certainly felt urges to e.g. connect the tips of my fingers/thumbs together (as in the classic Buddhist 'palms up' meditation mudra), or touch the tip of my tongue to the roof of my mouth ("Khechari mudra" in kriya yoga) while meditating.
Some yogis (ahem) even go so far as to cut the thin bit of skin that connects the tongue to floor of the mouth so that it can be pushed up inside the nasal cavity, behind the soft palette to directly touch the bones between the nostrils. The urge to do this can be great, and apparently can lead to feelings of ecstatic bliss. I feel the urge, but alas, my tongue can't quite hit the spot yet :(
But even just touching the tongue to the roof of the soft palette can let you feel a strong increase in tingles entering the centre of the head.
So as with much of religion, any sort of communication/symbolism related to mudras come later, and are probably created by people unaware of their biological origins.
Mudras are one of the first things that you learn when you start Bharat Natyam.
Most of the beginner classes start with practicing the Mudras.
I like to think of them as counting numbers in Math.
I might have picked this up from crystal-nonsense contexts, but certain traditions associate numbers with everything, or if not numbers, then the chakras or organs of the body.
Performing mudras as part of meditation can be a kind of physical mnemonic device, to help focus on whatever concept the mudra is meant to represent.
You could think of praying with hands together as a kind of mudra - posing your hands to access a certain state of mind.
I couldn't say how much overlap there is between chinese qigong and classical indian dance, but probably not none.
It's a fairly comprehensive write-up. I'm mostly familiar with the Hatha Yoga context of mudras.
There's also a few dozen books on the topic. I'd stick to the older more original texts if you want a real understanding, and stay away from the more modern new age fluffy bunny "crystal mudras" nonsense.
