Sahasrara = thousand, infinite
The Sahasrara Chakra is located on the top of the head. It is also known as the “Thousand-Petalled Lotus”, “Brahmarandhra” (the door to God) or the “Centre of a Million Rays” because it radiates like the Sun. No other light comes close to the brilliance of the Sun. In the same way, the energy and radiation of all other Chakras pale in the radiance of the Sahasrara Chakra.
In the Sahasrara Chakra exists an important power - Medha Shakti. Medha Shakti is a hormone that influences brain functions such as memory, concentration and intelligence. Yoga exercises can activate and strengthen Medha Shakti.
The Sahasrara has no special colour or quality. It is pure light, which contains all colours. The energy of all Nadis unites in this centre, like the waters of a thousand rivers pouring into the sea. Here is the seat of Shiva, the Supreme Self. The awakening of the Sahasrara Chakra means revelation of Divine Splendour and attainment of Supreme Consciousness. Just as night disappears with the rising of the Sun, ignorance fades with the awakening of the Sahasrara Chakra.
This Chakra represents the goal of Yoga, Self-Realisation and God-Realisation, where the individual soul unites with Cosmic Consciousness. One who gains this is liberated from all Karmas and achieves Moksha - complete liberation from the cycle of rebirth and death. In meditation the Yogi reaches Nirvikalpa Samadhi (the highest level of Samadhi) at the Sahasrara Chakra, where the mind finally comes to complete stillness and finds fulfilment in the union of knowledge, the knower and the object of knowledge.
In the Sahasrara Chakra the thousand-petalled Lotus blooms as a symbol of complete, unfolding Consciousness. The Divinity of this Chakra is Shiva in the form of pure, Supreme Consciousness. The corresponding element is Adi Tattva, the Supreme, spiritual Tattva. The Mantra is the same as for Agya Chakra, the original sound OM.
More about Exercises and Meditations for Sahasrara Chakra read here.