While in the United States the term “tantra” is often used to refer to sexual techniques that trigger mystical experiences, or mystical techniques that trigger heightened sexual experiences the actual definition is that it refers to the esoteric traditions of Hinduism and Buddhism. So “tantra” is not the formal doctrine of those religions but the occult practices undertaken by some Hindus or Buddhists often conceived of within the context of those religions, as far as these practitioners are concerned; you could consider this analogous to the thaumaturgy practiced by adherents of Vodoun, Christianity, etc. This is not to deny that the tantra pursued by some groups includes sexual techniques and that some groups focus on same. But it’s not the norm. Here’s an article discussing how “Neo-Tantra” arose in the U.S. and the impact it’s wound up having on Hindus and Buddhists in the countries where these religions/philosophies first arose.