Psychology in Greek means the science of the soul. Vedic psychology is also related to the soul. The soul makes matter function. Vedic psychology deals with the question how the soul perceives this world.
God has two types of energies manifest in this world. Ksetra and ksetrajana – the field and the knower of the field. One energy is made of matter, the other is conscious.
Matter is manifest at three different levels:
The level of the mind
The level of the senses
The level of the physical elements
Matter is acit, and does not have consciousness. The soul or purusha comes into contact with the physical world of matter only indirectly, through the subtle elements of citta (unconscious mind), buddhi (intelligence) and ahankara (ego), citta is the store house of experiences, which contains subtle impressions, samskaras. Whatever we experience is stored in the citta throughout the different forms of life a living entity goes through. The vision of the world is based on our samskaras which we modify with every experience.
Buddhi or intelligence is the conscious mind. Manas is the subconscious mind which works through comparison.
Ahankara or I-consciousness (ego) is that which gives us the feeling of an individual being, different from everything else. It consists of two parts: The functional (related to functions inside or outside of our body) and the representational part, which gives identity. Those who can transcend ahankara can get into contact with cosmic intelligence.
Ego, unconscious, conscious and subconscious minds are all interrelated.
Prana is energy carried through life air. Life air is the air functioning inside the body. The soul can infuse consciousness into citta through prana.
Although not perceivable to us, consciousness is actually everywhere and pervades everything. This world is a combination of ksetra and ksetrajna, or in terms of Sankhya, purusha and prakriti. What is holding the world together is Paramatma, the immanent being and controller of all beings.