When people talk about tantra today, they're not normally talking about the tantric religion or the history of the tantric tradition. They're talking about sex. Weird, vibrating, hour-long-orgasms-without-ever-touching sex. Bodies bent into positions humans shouldn't even be able to get into sex. But tantra is actually an entire tradition found in some Indian religions - and the history of tanra is fascinating, if a bit confusing.
In fact, Buddhism and Hinduism both have had strong associations with tantra. But the more you look at tantric tradition facts, the more you see it's a complex, unwieldy, and almost undefinable tradition that goes back hundreds and hundreds of years. There's astrology; there's yoga; there's imagining yourself as deity - it's a belief system, which, in its way, encompasses everything a strong belief system should. And yes, there's some pretty weird sex stuff - in some sects, anyway. So you won't be disappointed.
At the most basic level, when someone asks "What is tantra?", you're going to find it difficult to get a straight answer. In around 1,000 CE, the tantrik scholar and guru Rāma Kaṇṭha defined it as:
"a divinely revealed body of teachings, explaining what is necessary and what is a hindrance in the practice of the worship of the Divine; and also describing the specialized initiation and purification ceremonies that are the necessary prerequisites of Tantrik practice. These teachings are given to those qualified to pursue both the higher and lower aims of human existence."
Others point out the etymology to explore the definition, explaining:
"The word 'tantra' is derived from the combination of two words 'tattva' and 'mantra'. 'Tattva' means the science of cosmic principles, while 'mantra' refers to the science of mystic sound and vibrations. Tantra therefore is the application of cosmic sciences with a view to attain spiritual ascendancy."
So perhaps it's unsurprising that the shorthand for tantra is basically living at one with the divine or, alternatively, finding a route to divinity in life. There are hundred of teachings, spanning centuries and different religions, and sometimes "tantras" are also used to refer to some of the scriptures that the teachings come from. So the term refers to both the tradition and, in some cases, the physical teachings.
Ok, so you really can't talk about tantra without bringing up the sex issue. Is it about sex? Does it give you 10-hour orgasms?
Historically, there existed a strain of tantra called the left-handed (vāmācāra) tantric traditions, which were associated with violence and sex. The Vidyāpīṭha tantras and the later Kuala tradition, for example, were specifically centered around violence and sex. The idea was to break the practitioner free from convention.
Although these weren't the only strains that celebrated sex and violence, there were five particular markers of these traditions:
"1. Erotic ritual with a female companion" (AKA the sexual stuff that many people nowadays associate with tantra)
"2. Sanguinary practices for the propitiation of the fierce gods Mahābhairava/Bhairava and Cāmuṇḍā," (or, bloodletting and blood sacrifices made in order to keep the gods appeased and happy)
"3. The notion that supernatural powers may be attained through the extraction by yogic means of the vital essences of living beings," (in other words, the idea that yoga practice could create oneness with other living beings)
"4. Initiation through the consumption of consecrated liquor," (i.e. drinking particular liquors to get closer to the gods and other living beings)
"5. The centrality of states of possession," (the idea that the consciousness of the gods can enter a tantra practitioner's consciousness)
Sounds pretty brutal. And this notion is much of what the modern concept of tantra has been reduced to. Not only in the West - even today in India, the word tantra “is frequently used to conjure notions of effective black magic, illicit sexuality, and immoral behavior."
Although there were sexual rituals in some sects of historic tantra, they aren't really the way most people think of tantric sex now.
Why was sex a part of tantra in the first place? Well, tantric believers are certainly not the first - or the last - group to think that an orgasm produces a state of enlightenment, a touch of divinity. But this was only practiced by some sects. What can be seen in the West today is 'neotantra' or 'California tantra,' which involves breath control and self-discipline, but it's usually more about bonding with your partner and delayed (and intensified) orgasms than achieving any enlightenment or religious bliss.
Many threads of tantra have a strong emphasis on a relationship to a guru, or spiritual teacher. In fact, the importance of this is laid out in The Fifty Stanzas on the Guru (Gurupañcāśikā). But this is another area of tantra that is often used to showcase the sexual nature of the practice, albeit not necessarily correctly.
Tantric guru Sadhguru explain: "The Guru-shishya relationship is to deliver the shishya to a higher dimension of consciousness, not trap one into the compulsive nature of sexuality. Above all, this sacred relationship is definitely orgasmic, but not sexual. I am talking about upgrading your technology. You don’t have to huff and puff to get into an orgasmic state. If you sit with your eyes closed, you can drip with orgasms in every cell of your body. Those who have failed to achieve an orgasmic state of existence will associate an ecstatic state with sexuality because that’s probably the highest level of experience they have known."