Tantra is a collective title that covers a vast range of practical teachings leading to the expansion of human consciousness and the liberation of primal energy (Kundalini). The unifying principle behind the diverse systems of tantra is that the material world and its experiences can be utilised to attain enlightenment.
Many movements today describe tantra as sexual practices promising longer and better orgasms, increased stamina and ecstasy, but this is a shallow and paltry echo of the Tantric Tradition. The real Tantra aims to awaken Kundalini, the dormant potential force in the human personality.
Although there are many branches of Tantra, the practices common to all systems leading to transcendental awakening are mantras (vibrational tuning through sounds), yantras (concentration symbols to liberate the consciousness), chakras (realisation of psychic centres), mandalas (perception of macrocosmos in microcosmos), tapasya (practices of self-purification), Raja Yoga (integral yoga), pranayama (yogic breathing practices), self surrender, shaktipat (transmission of energy) and tantric initiations (a process incorporating all of the above imparted by the qualified master to a deserving disciple).
Tantra advocates a pattern of life which integrates the faculties of the intellect and the heart. The faculties of the intellect are discrimination and concentration, and those of the heart are seeing the unseen, having glimpses of the transcendental or cosmic consciousness beyond the material.
Literature on this subject includes A Systematic Course in the Ancient Tantric Techniques of Yoga & Kriya and Kundalini Tantra.