Supermind can be described in simple terms as the Mind of God as the Creator. It is the Omniscience and Omnipotence of God and through it links the One Supreme Divine with the cosmos as well as each individual element of creation. It is where our individual souls emerge and the original blueprint of our individual life as well as of the creation is found.
The Supermind releases Its Knowledge and Power into creation by putting forth certain delegate powers of the One Divine. This delegate of the Supermind is termed the Overmind where we see the One Divine in the unity of His fourfold aspects differentiates them into a power and Knowledge inherent in Existence (Brahma), power and Knowledge operating as Consciousness (Vishnu), power and Knowledge operating to create and dissolve or destroy (Shiva), power and Knowledge sustaining the world play through the various degrees and shades of Ananda (Krishna). The Overmind is the plane of the original Gods.
But between the human mind as it presently is and the Overmind there are steps of increasing vastness of light and Knowledge and power so that we can be gradually prepared to finally meet the Creator without veils. Then He can work directly in us and through us and not through the veils of ego and ignorance as now. These ascending steps are the Higher Mind where Truth is seen as symbols, the Illumined Mind where one sees the Truth through inspiration and revelation rather than analysis. Finally, between the Overmind and the Illumined Mind there is the Intuitive Mind which sees the hidden truths like lightning shows things covered in darkness.
There are other related terms such as Sacchidananda which describes the One Supreme, Parabrahman which is the Absolute, Vidyamayi Maya which is a power of differentiation of forms in the backdrop of oneness and Avidyamayi Maya which is a power that fixes the limits of each form.in such a way that it perceives itself separate and divided from the rest.
There are many other terms but we can leave them for now.
Affectionately,
Alok Da