The material world is all feminine. The feminine engergy makes the non-manifest, manifest. So even men (are of the feminine energy). We have to relinquish our ideas of gender in the conventional sense. This has nothing to do with gender, it has to do with energy. So feminine energy is what creates and allows anything which is non-manifest, like an idea, to come into form, into being, to be born. All that we experience in the world around us, absolutely everything (is feminine energy). The only way that anything exists is through the feminine force.
A unifying factor between the different traditions and lineages of Tantra, is that it is feminine in nature. It acknowledges the feminine as the basis from which all the practices spring. Therefore, Tantra is by its nature, the understanding that all phenomenal existence, the universe, or cosmos, that we experience is feminine in nature.