Tantra is a popular topic in both Hinduism as well as Buddhism. The word Tantra is taken from the two roots, "tanoti", to extend or stretch and "trayati", which means, liberation.
According to Hindu tantrism, the entire universe is considered to be the divine stage where Shiva and Shakti carry on the drama of life. Tantra deals with ritual and spiritual practices to attain the grace of that Shakti, with the aim at achieving liberation from darkness of ignorance, thus also attaining immortality.
Tantra originated in the early centuries CE and deeply influenced the Hindu Buddhist, Jain and Sikh religions as well. Tantra is quite an abstract belief system. Also, different traditions are not even consistent with each other. It is not a single coherent system. It is rather a tradition that gradually evolved from an accumulation of practices and rituals, in order to attain the grace of the divine.
Tantra has its roots in mysticism