Yoga, in the traditional sense of the word, is a path or practice leading to enlightenment or God-realisation. There are three main types of yoga. Bhakti Yoga, Karma Yoga and Jnana Yoga. Many scholars also include Raja Yoga, first elucidated by Patanjali in his Yoga Sutras.
Resources:
Yoga – General
What is Yoga? – by Sri Chinmoy
Bhakti Yoga
Bhaktas consider love and devotion to be the fastest route to reach the Highest.
Bhakti Yoga – by Swami Vivekananda
Bhakti Yoga – by Sri Chinmoy
Karma Yoga
Practitioners of Karma Yoga attempt to make spiritual progress whilst staying in the world, by performing actions without attachment to their results.
Karma Yoga – By Sri Chinmoy
The Ideal of Karma Yoga – by Swami Vivekananda
Jnana Yoga
Jnanis seek to find the Highest through knowledge
Jnana Yoga – by Sri Chinmoy
Raja Yoga is considered one of the six main schools in Indian philosophy, and as such is discussed in the Indian philosophical schools/darshanas section.
Introduction to Patanjali’s Yoga Sutras – by Parlan Fritz
Raja Yoga – by Swami Vivekananda