Situated at the crown of the head, and not a chakra.
Sahasrara literally means ‘one thousand’, and refers to its lotus which consisted of one thousand petals. These one thousand petals, has the fifty letters of Sanskrit twenty times over.
In the centre of the lotus, there is a shining jyotirlinga, which symbolizes pure consciousness. Here union of Shiva and Shakti takes place, union of consciousness and matter and energy, individual soul and the supreme soul. Once Kundalini awakens in mooladhara chakra, it ascends through the chakras to Sahasrara and merges into the source where it came from, whence originated. Matter and energy merge into pure consciousness I a state of intoxicating bliss. When Self-realization occur, Kundalini and sahasrara meet, the individual dies to this world. It doesn’t mean the physical body dies, but rather the mundane awareness or individual awareness, the death of name and form. The experience, experiencer, and experienced are the same one! No more duality but unity! Single awareness.
Sahasrara is both formless (nirakara) and with form (akara), yet it is also beyond, and therefore untouched by form (nirvikara). It is shoonya, or in actual fact, the void of totality. Sahasrara is Brahman, it is nothing and everything at the same time. We can’t say anything about Sahasrara without limiting it, or categorizing it. The merging of consciousness and Prana.
Once attained, the Yogi gains supreme knowledge and passes beyond life and death.When this occur, this union is exactly what Sri Sage Patanjali is referring to as Samadhi.
Om Tat Sat