Bindu Chakra comes from the "point of origin" or the "drop of creation" because bindu is loosely translated as "point" or "drop." It is not mentioned as a chakra in most tantric systems, because of its purely occult nature. It's awakening is not so much an "awakening" as it is a "release" or "flow."
This terminology is important because the tantrik must focus on the release (say of water from the chutes of a dam) or the flow (say of wind from a tornado). Some consider this to be the source of creation and others the origin of consciousness. Once again, because of its occult nature, it can only be understood as the point of creation - of life, consciousness, intelligence, knowledge, etc. And it is represented symbolically as the sperm, drop of mother's milk, ray of light, a germinating seed, and the like. If modern knowledge were to be used, then it could be the point source of infinite energy from where the cosmic Big Bang occurred.
While Bindu is a flow it is also experienced as a "taste of nectar." One must not confuse taste with the actual taste - let's simply say the "sensation" of nectar. The Tibetan Buddhism bindu is a tattva that is composed of drops and the winds. The release or flow of this bindu fluid/nectar is vital to the awakening of the sahasrara chakra.
In a simplistic manner, bindu chakra is said to be the point of origin and the ultimate point of return. Our creation arises from the bindu and will end in it. This is not only the origin of human life but of all life, and when life ceases, it will return to the bindu. If the vishuddhi chakra is the first intellectual chakra, then bindu is the first occult chakra. Its manifestations include the experience of god, super god, Kali and Shiva.
Connection with the Throat Chakra
Bindu is interconnected with vishuddhi chakra in the same way that the small centers of the digestive tract are linked with manipura chakra, and aspects of the urogenital and reproductive systems are connected with swadhisthana and mooladhara chakras. In the same way, the small centers of the circulatory and lymph systems are integrated into anahata chakra and so forth. In every situation, the link is mediated by the particular set of pathways associated with that chakra.
Note: These may be nerves at times but should not be confused for nerves. It is a big mistake to make exact comparisons with modern human physiology.
Bindu and vishuddhi are connected through the nasal canal. If you should make a comparison, then the Ear-Nose-Throat system connects these two chakras. Thus, when awakening occurs in vishuddhi, it simultaneously releases the divine nectar of bindu.
The representative location of the bindu chakra is at the back of the head directly opposite the forehead (ajna chakra). You can also feel this as a slight concave depression in your cranium at the back of your head. These locations are merely a means to focus your concentration or Bindu Chakra Meditation on the particular chakra. There is no scientific or actual connection. Modern tantriks desperately try to make such associations in the same as religious people use Science to justify the existence of god. Needless to say, it would be easier to accept Tantra and Kundalini Tantra as a system with its own terminology, system of symbols, and philosophy
In Yoga practice, the khecari mudra (kechari mudra) stimulates the bindu nectar. Please remember that this is symbolic and no fluid is actually secreted!
The Symbol of Om also includes the representation of bindu in its uppermost part, which is a little point over a crescent moon. Therefore, bindu visarga flows/awakens, the cosmic sound of Om is heard and one realizes that the source of all creation, emanates from the bindu stage and crescent moon over the sign of Om.
The Poison Center
Bindu produces nectar and it also creates toxins. Since Tantra does not judge between good and bad, the nectar is as divine as it is evil. It is only in the moral domain that something becomes evil. For example, sex is pleasurable but sex outside of marriage is considered immoral (and perhaps even illegal). Similarly, bindu nectar provides the catalyst for enjoying pleasure but does not discriminate between human morality and societal laws.
When a Yogi has puriﬁed his entire body via Hatha Yoga and vishuddhi chakra has been awakened then discrimination will automatically arise and control the digestion fo this nectar/poison. This is not the Shiva level of consciousness where the tantrik can consume the bindu fluid uncaring of its nectar/poison duality.
Understanding the bindu from the view of non-duality, makes us comprehend how the world splits into infite possibilities from the division of this indivisible point. This is similar to the Zero in mathematics: the origin which gives rise to infinte numbers - positive and negative - on all the possible axes.
Bindu suggests a point without measurement: a dimensionless centre or a location with dimensionless coordinates (0,0,0). Similarly, it is in this dimensionless space that consciousness arises. Consciousness is infinite and it is infinitesimal. It is the gateway to the infinite void or the domain of Shiva. It is Being and Nothingness: as consciousness expands, it overflows. But as consciousness contracts, it also reduces disproportionately. In Calculus, we approach 0 but never reach it. Thus, we approach nothingness but never reach it. We continue to maintain the same level of potency of consciousness even as we get smaller and smaller.
Shoonyata (Shunyata) is this tattva of experiencing smallness (really, really, really small) without any reduction in our consciousness. Some tantriks compare this to dreamless sleep - we are alive but there is no consciousness! Bindu stradles the zero and the infinte with equinamity, going from one to the other that no time travel machine can imagine!
It's the way through which conscious centers of man may realize the totality of sahasrara. This state of pure consciousness transcends the barriers associated with the chakras (from mooladhara chakra to ajna chakra) to attain samadhi. Please note that samadhi is a level that is achieved and not a level that is reached. The difference is like climbing a hill to reach the peak and jumping into a rapid river that carries you to the mouth of the waterfall!
The Guru Inside
There are essentially only two kinds of human beings - people who are extroverts and people who are introverts. Except for pathological states, we all lie somewhere between the two extremes. However, in Kundalini Yoga and any other tantric practice, one has to start an inward journey. One has to analyze social and domestic norms to ascertain their validity and superfluousness. Nirvana is not attained by practicing social and religious rituals! A guru may tell you that, but not a tantric guru.
The Sanskrit word guru is only superficially translated as teacher: a tantric guru is not someone who teaches; he is someone who awakens your consciousness, shows you the path, and pushes you down a steep mountain. He teaches you true freedom! He shows you inner harmony: this harmony is not one of passive lethargy but a comfortable and confident vibration. The third eye chakra awakens due to the bindu fluid/wind catalyst and the same catalyst then awakens sahasrara.
Similarly, the guru chakra is said to awaken you and makes you a yogi. This guru chakra is not within you but in your guru - it is akin to making your guru a part of you. However, quite often a Hatha Yoga practitioner will become a part of the guru instead and this is detrimental to the student's growth and study. In Tantra Yoga, a tantric guru will be wary of this and never allow the student to make this mistake.
When this nectar/poison flows it goes from red to white signifying the blood energy and the life force of creation to the white of ash or the void of life cessation. This life cessation is not death but the end of life as we knew it. Perhaps a domestic life, perhaps a life full of worry and care, or a life full of meaningless, materialistic pursuits.
White and Red
The white bindu and the red bindu signify the cosmic seed from which all things grow and manifest. It is frequently linked to male sperm simply because in the tiny bindu of a single spermatozoon, combined together with the minute female ovum, a new life develops. The act of conception is a perfect symbol of the principle of the bindu.
The transition from red bindu to white bindu is not metamorphosis - it is a transmutation! The red bindu flow represents the evoked but dissipated state of Kali while the white bindu is similarly the dissipated state of Shiva.
This dance between Kali and Shiva is the path of Vama Marga (Tantric Sex) that tantric lovers choose for their enlightenment. In these states, both are trying to gain supremacy in the same way as the bindu fluid is trying to be nectar or poison. However, this state does signify the start of the final two stages of Kundalini awakening: the awakening of ajna and sahasrara. The sushumna nadi is ready to carry the nectar onwards!
As mentioned earlier, the occult nature of bindu does not allow easy description in words. Modern scientific symbols are also used, such as DNA, sub-atomic particles, and the like. This is simply an illustration of the deep intelligence and infinite potential which may be condensed in a very small point. In Tantra, each bindu manifests some part of the universe: it could be one atom or one brain or one mindscape created by the Internet! This Shakti is a reflection of the underlying substratum of inactive consciousness.
The intention of the tantric system is to bring about a combination of Shakti - the individual manifested power, together with Shiva - the inert, underlying universal consciousness.