Prakruti is composed of three components, called gunas. The term guna here means a ‘component factor’. The trigunas are:
Whatever is pure and fine is Satva. It is the essence of a thing by which it manifests itself in buddhi (intelligence). In the world of consciousness such manifestation is essential for the entity of the thing in question.
Whatever is active in a phenomenon is Rajas.
Whatever is passive is Tamas. It is mass in inertia. It offers resistance.