Tantras: Tantra is said to be derived from tattva (essence or truth) + mantra (incantation/holy formula) – meaning that Tantra elaborates the essence of the science of mantras. The term Tantra is also translated as “loom” – meaning that Tantra elaborates how the fabric of reality is woven together. In Hinduism, there are Tantric texts belonging to various schools. Along with the Vedic canon, the Tantric canon has shaped much of modern Hindu beliefs and practices.

Discussion: Hinduism has two bodies of primary texts: the Vedic canon and the Tantric canon. The Vedas are called Nigama (going to), and the Tantras are called Agama (coming from) – together the Nigama-Agama texts form a complete circle of knowledge going to and coming from the Divine. The Tantric scriptures are divided into three schools – Shaiva, Shakta and Vaishnava. Tantric texts of Shaivism are generally referred to as Shaiva Agamas, those of Shaktism are referred to as Shakta Tantras, and those of Vaishnavism are referred to as Pancharatra Samhitas. The theologies, ritual practices, worship protocols, temple liturgy, yoga and philosophy of the Shaivas, Shaktas and Vaishnavas are guided by their respective Tantras. Elements of the Tantras, especially those involving theory and practice of temple worship, are also accepted by the Smartas. Tantric texts are famous for their esoteric teachings, and freely use external symbols to aid in the understanding of deeper concepts. Among other things, the Tantras provide the theory and rationale for image worship in Sanatana Dharma.

References:
http://www.dlshq.org/teachings/tantrayoga.htm
http://www.haryana-online.com/Culture/tantra.htm
http://www.shaivam.org/agama.htm
http://www.hinduwebsite.com/hinduism...ures.asp#agama
http://www.dlshq.org/religions/agamas.htm
http://hinduwebsite.com/secretsofworship.asp
http://www.sacred-texts.com/tantra/sas/sas03.htm
http://www.srivaishnava.org/sgati/vo...20-%20part%201