This Fire Release technique appears to be initiated remotely upon placing the target in contact with a physical object such as a kunai or even a small toad, and can cause the target to spontaneously burst into flames. Regarded as the "Flames of Purgatory" (煉獄の炎, Rengoku no Honō), they are said to be inextinguishable by wind or rain, and burn so quickly that regenerative techniques cannot keep up with them, leaving the victim's body completely charred in mere moments. The flames can, however, be absorbed and sealed away.
"Samadhi" refers to a state of meditative consciousness. It is the last of the eight elements of the Noble Eightfold Path which is an early summary of the path of Buddhist practices leading to liberation from the painful cycle of rebirth.