Does not mean your brain, which is a physical organ containing about 100 Billion brain cells. These cells help in communicating thought vibrations to the sense organs and there by to the body. Mind consists of a static state and a dynamic state of displaying its energy. In a static state it, means Cosmic Self or Consciousness which is infinite also called as ‘Self or Atma’. In a dynamic state, few localised thoughts/imaginations leads to creation of ‘Subtle mind’ consisting of Manas, Buddhi, Chit and Ahankar which carries imprints from our previous actions.
Manas is a recoding faculty of all the millions or billions of imprints either from this birth or from previous births and hence can be called an Inner world.
Buddhi or intellect is the faculty which has the ability to discriminate right, wrong etc.
Chit is the faculty which chooses the path one way or the other after discrimination by Buddhi.
Ahankar or ego is the faculty in the dynamic state of consciousness which identifies with the sense organs or body, possessions, relationships etc.
Hence it is very important to keep the ‘Subtle mind’ pure by dedicating our actions in the outer world to divinity instead of being greedy and doing it for sake of satisfying our Ego. Due to our own desires in the past we moved from the static state of Divine Self, to have a Causal body ( few thoughts or desires) , then we created a Subtle mind/body and thereafter a gross body to fulfill our thoughts/imaginations. To control and purify our subtle mind, our sages have discovered the art of meditation.