Tantra is a spiritual and mystical path which essence is condensed in the first two verses of the 9th century “Spandakarika (Song of Vibration) of Kallata:”
1) Beloved Shankara (Shiva = unmanifested awareness), source of Shakti (=energy) opens his eyes and Universe resorbs into pure consciousness. He closes them and Universe manifests in him.
2) The vibration (Spanda), which is the very place of creation and return has no limit, because its nature has no form.

In those two verses lies the essence of the common ground of all Tantric beliefs.
There is no separation between the individual and the world. Consciousness without any form and any limit supports the Energy of the Universe which everything is made of. We are, at the same time, a conduit for this energy, and as well as its only reality. The microcosm represented by the Tantrika is a reflection of the Universe and, by itself alone, contains the macrocosm (the Universe or the Creation). Accessing the sensation of the vacuity that underlies anything, as well as moving away from the illusion that the individual is separated from the rest of the world, allows the perception of Shakti, the universal Energy.
The path of the Tantrika is a path of awareness (Shiva) that leads to the perception of Energy (Shakti) and non-duality (Advaïta).