Hatha yoga or classes that are called yoga classes focus on physical Asanas (posture/poses). Those are a small part of what Yoga means in traditional Hindu scripture and belief. The following represent the ancient paths of Yoga that through practicing one can reach the summit of the mountain or Moksha (liberation).
Jnana Yoga: Jan means to know deeply what is real and true; to penetrate illusion. This path to knowledge requires focusing on that which is not changing; the absolute truth of who we are. To realize that we are Brahman is Jnana but also to see ourselves everywhere in Jnana. Jnana yoga requires the use of the mind in dissolving ignorance by reading and studying ancient texts. It also involves exploration of our nature by pealing false identities.
Karma Yoga: Karma is the sum total of our deeds both in this life and the one before. Karma explains how every action comes from a cause producing further effects. Karma Yoga is then the transformation of action to that which is without expectation or attachment, to selfless action that purifies the heart. All action (physical, mental and spoken) ought to be dedicated to spiritual ends without expectation of any fruits. Only this way will one reap love.
Bhakti Yoga is the yoga of devotion. Bhu is to share in love. This mystical path requires attachment to God and regular worship in every situation. Bhakti Yoga softens the heart. The Bhagavad Gita provides a number of interesting positions on Bhakti Yoga, for instance 9.34: Fill your mind with me; love me; serve me; worship me always. Seeking me in your heart, you will at last be united with me.
Raja Yoga: this yoga is royal as it aims to quiet the master function of the mind; the production of thoughts and ideas. Raja yoga disciplines the mind and senses and removes impediments to discovering what I am. Meditation is the practice in Raja Yoga. Pad I verse 2 of the Yoga Sutra speaks of yoga as the cessation of the turnings of the mind and Chapter six in the Bhagavad Gitta emphasizes the importance of meditation, especially in verse 46 where it says “Meditation is superior to severe asceticism and the path of knowledge. It is also superior to selfless service.” Meditation is a very old practice that may date back to the Shvetashvatara Upanishad, which provides ways of meditation section II.