Kundalini is energy believed to be coiled at the base of the spine. Kundalini also refers to a meditation system designed to release this energy. When people have a kundalini awakening, more prana (chi) is held and runs through their nervous system.
It is said that yoga can unblock the energy from the Root chakra and let it travel up the spine to allow you to connect with your soul and higher consciousness.
This type of yoga was originally called Raj or Laya yoga and was passed down from one guru to another.