Search 'Tantra' in any Western city and you will find massage parlors offering 'tantric massage,' workshops promising 'orgasmic meditation,' and weekend retreats teaching 'sacred sexuality.' With rare exceptions, these are about as truly Tantric as a fortune cookie is truly Confucian. They pull one piece, the positive attitude toward sexuality, out of a vast and demanding spiritual tradition and sell it beyond recognition. Real Tantra is one of the most rigorous, demanding, and deep spiritual paths in human history. It includes long philosophical study, years of initiation under a qualified guru, complex ritual using sound (mantra), form (yantra), and gesture (mudra), advanced yoga and meditation, and, in the left-hand Tantric schools, the use of taboo-breaking ritual elements including sexuality, as specific, carefully structured tools for taking apart the ego's usual ideas of what is sacred and what is profane.
The word 'Tantra' comes from the Sanskrit verb tan, meaning to extend, expand, or weave, plus tra, a suffix that means a tool or instrument. So Tantra literally means the tool of expansion: the technology for stretching consciousness beyond its usual limits. The Tantric scriptures (the Tantras and Agamas) are a huge, varied body of texts, most written between the fifth and twelfth centuries CE, covering cosmology, philosophy, ritual, yoga, medicine, astrology, and practical methods for spiritual growth. Far from being mostly about sex, the great majority of Tantric practice is meditation, mantra repetition, visualization, breathwork, and the philosophy of non-duality. The sexual practices are one small category inside a much larger system, and they were reserved for highly advanced initiates, never handed to beginners.
The Tantric tradition is split between the Dakshinachara (right-hand path) and the Vamachara (left-hand path). The right-hand path swaps in symbolic or inner versions of the taboo-breaking parts of ritual, imagining wine instead of drinking it, imagining union instead of physically enacting it. This is the form of Tantra practiced by the large majority of Hindus who identify with the tradition. The left-hand path, practiced by a small minority of advanced initiates in specific lineages, uses the actual taboo-breaking elements, including sexuality, intoxicants, and ritual meat-eating, as direct tools for breaking down the practitioner's usual sorting of the world into pure and impure, allowed and forbidden.
The reasoning behind the left-hand path's use of sexuality as a spiritual tool is philosophically sharp. In the Tantric non-dual view, the absolute reality (Brahman, or Shiva-Shakti) is the same as everything that appears. Nothing is not sacred, because nothing is not the divine expressing itself. The ego, though, keeps elaborate rankings of sacred versus profane, clean versus dirty, spiritual versus carnal. Those rankings are exactly the walls of separation the Tantric path aims to dissolve. Using sexuality, the most consistently taboo and therefore most boundary-heavy category in most religions, as a sacred practice is a direct and efficient way to take apart the ego's categories. But this only works with the right container: the right initiation, the right instruction, the right partner, and the right inner development. Without those, it produces not freedom but confusion.