The practice is at least 3000 years old, and its origins can be traced to India. It is considered to be a philosophical system. Bhakti yoga is a way of devotion of love and faith directed to God. It uses chants and worship, Dhyana yoga is a method of concentration. It is a purely mental discipline leading to trance states.
Karma yoga is concerned with selfless work and good deeds.
Charitable acts are accomplished by individuals who follow this path. Kriya yoga is primarily concerned with religious action and ritualism. Kundalini yoga theorizes potential energy coiled up in the nervous system, which can be released with the recitation of sacred mantras. Hatha yoga is the most familiar to Westerners. It is the path of health using exercise as a means to mental and physical harmony.