In Hindu religion, Siddhas are realized souls who have acquired self-knowledge. Though they appear to be in bondage to the physical body, they are above body, mind and intellect. Being one with the all-pervading absolute Brahman, they are in a state of unending bliss. They are always in a state of meditation, being one with the Self.
The basic characteristics of Siddhas are their identification with the absolute Brahman and being one with the universal consciousness.
Siddhas posses several superhuman powers called siddhis. These are anima, garima, mahima, laghima, prapti, prakamya, isitvam and vasitvam. A person who has acquired any of these siddhis is called a siddha.
There are instances of siddhas moving inanimate objects and giving life to the dead. Their words come true. They can even read the minds of people. Their powers are often used for the good of individuals or the society.
According to Vayu Purana, siddhas are the residents of bhuvarloka, a place located north of the sun and south of the saptarshi mandal (a constellation of seven stars).