Everything manifests as a duality. Can you think of the idea of hot, if there were no cold?
In Indian philosophy, Shiva and Shakti are like this, the one does not exist without the other.
Shakti, from the Sanskrit "Shak" - "to be able", is the enabler, the dynamic force which manifests the Universe.
Shiva is the transcendent ground of being.
Without Shakti, the ground of being remains unmanifested and all that we call our physical reality would not exist.
Different cultures have intuited Shakti by different names, but most have a divine feminine, a Great Mother figure.
Have you ever moved amongst great, old trees and felt an undeniable force emanating, a force that evoked feelings of reverence, even though you may not have had a philosophical or spiritual framework to reference it? At such times we are sensing into Shakti.
In yoga we sensitise ourselves to flows of energy in our bodies. Any flow of energy is Shakti.
So although Shakti is characterised as feminine and Shiva as masculine, both are present within all of us, men and women.