Tantra, what is it?

In the words of Osho….
The word ‘tantra’ means the capacity of expansion, that which goes expanding. Sex shrinks you, Tantra expands you. It is the same energy, but it takes a turn. It is no longer selfish, no longer self-centered. It starts spreading – it starts spreading to the whole existence. In sex, for a moment you can attain to the orgasm, and at a great cost. In Tantra you can live in the orgasm twenty-four hours a day, because your very energy becomes orgasmic. And your meeting is no longer with any individual person: your meeting is with the universe itself. You see a tree, you see a flower, you see a star, and there is something like orgasm happening.
PHIOSOPHIA PERENNIS, Vol. 1, Chapter 6 – Osho