The Indian Tantras, which are numerous, constitute the Scripture (Shastra) of the Kaliyuga, and as such are the voluminous source of present and practical orthodox "Hinduism." The Tantra Shastra is, in fact, and whatever be its historical origin, a development of the Vaidika Karmakanda, promulgated to meet the needs of that age.

Shiva says: "For the benefit of men of the Kali age men bereft of energy and dependent for existence on the food they eat, the Kaula doctrine, O auspicious one! is given" . To the Tantra we must therefore look if we would understand aright both ritual, yoga, and sadhana of all kinds, as also the general principles of which these practices are but the objective expression."

The word "Tantra" means "treatise", and is applied to a variety of mystical, occult, medical and scientific works as well as to those which we would now regard as Taantrik. Most tantras were written between the 10th and 14th centuries CE.

While Hinduism is typically viewed as being Vedic, the Tantras are not considered part of the orthodox Hindu/Vedic scriptures. They are said to run alongside each other, The Vedas of orthodox Hinduism on one side and the Agamas of Tantra on the other. However, the practices, mantras and ideas of the Atharva Veda are markedy different from those of the prior three and show signs of powerful non-Aryan influence. Indeed, the Atharva Veda is cited by many Tantra texts as a source of great knowledge.

it is notable that throughout the Tantras, such as the Mahanirvana Tantra, they align themselves as being natural progressions of the Vedas. Tantra exists for spiritual seekers in the age of Kaliyuga, when Vedic practices no longer apply to the current state of morality and Tantra is the most direct means to realization. Thus, aside from Vajrayana Buddhism, much of Tantric thought is Hindu Tantra, most notably those that council worship of Lord Shiva and the Divine Mother, Kali.

A Tantra typically takes the form of a dialogue between the Hindu gods Shiva and Shakti/Parvati, being that Shiva is known in Hinduism as being 'Yogiraj' or 'Yogeshwara,' 'The King of Yoga' or 'God of Yoga' and that his consort is known to be his perfect feminine equal. Each explains to the other a particular group of techniques or philosophies for attaining moksha (liberation/ enlightenment), or for attaining a certain practical result. [Agamas are Shiva to Shakti, and Nigamas are Shakti to Shiva.]

This extract from the beginning of the Yoni Tantra gives an idea of the style.

Seated upon the peak of Mount Kailasa the God of Gods, the Guru of all creation was questioned by Durga-of-the-smiling-face, Naganandini.

"Sixty-four tantras have been created O Lord, tell me, O Ocean of Compassion, about the chief of these."
Mahadeva said:
"Listen, Parvati, to this highly secret one, Dearest. Ten million times have you wanted to hear this. Beauteous One, it is from your feminine nature that you continually ask me. You should conceal this by every effort. Parvati, there is mantra-pitha, yantra-pitha and yoni-pitha. Of these, the chief is certainly the yoni-pitha, revealed to you from affection."