Yoga is divided into many kinds on account of its actions. Beside the main paths of Yoga which are Karma Yoga, Jnana Yoga, Bhakti Yoga and Raja Yoga, there are another paths such as Nada Yoga, Laya Yoga and Hatha Yoga.

KARMA YOGA

is a selfless deed. It is a good and effective companion in life, which can restore the most valuable qualities in people, the kindness and the warmth. The altruistic action will lead every being who gives without expecting to get anything back to liberation (self realization), it will bring serenity in one’s heart and piece in one’s mind.
Many people in our society share their lives and what they have reluctantly with others, instead they lead a retired life in their cocoon enslaved by material possessions.

A selfless deed frees us, makes our lives richer and transforms our ego.
It is like love, it is not the word but the deed.

The Bhagavad Gita, a part of the Mahabharata, the major Indian epic of ancient India, talks about karma yoga.

JNANA YOGA

or Gjana Yoga is a systematic way to self-realization and liberation. Jnana Yoga is about the discernment to recognize what is true and what is untrue. This path leads to the level of existence where our lower nature ends and where we will be one with everything. It is the issue of the Advaita Vedanta, or non-duality.
The Sanskrit word Vedanta means the end of knowledge and relates to the transcendental knowledge, not intellectual.

This path of knowledge is a long way of wisdom which can be reached only step by step, and that is only possible with a lot of honesty to its own self and a lot of self discipline. The insight is the child of knowledge. Experience and knowledge become one.

This path is not for people who are prone to delusions and exaggerations because the false identification with what one is not can lead to deep confusion.
Jnana Yoga is pure knowledge.

All four Vedas, the Rig Veda, Sama Veda, Yajur Veda and Artharvaveda, the collections of texts which the Upanishads are a part, speak about Jnana Yoga.

BHAKTI YOGA

is the path of devotion to God.

As in all other aspects of existence, in Bhakti Yoga is also important to be honest with yourself. If practiced misunderstood, the practice can easily become begging instead of prayer.
He who practices Bhakti Yoga with an open heart (instead of begging with closed heart) can transmit his love to God to all beings. In life of one true Bhakti will be no more place for doubts and conviction, he will see and feel love in everyone and everything.

NADA YOGA

Just as there are the gross and subtle manifestations of Prana, the sound has its coarser and finer manifestations.
Nada Yoga is yoga of finer transcendent sound vibrations. The finer and open awareness, the finer the reception of sound vibrations.
In our subtle bodies there are energy centers (chakras), where the energy channels (nadis) cross. Through the chakras the electrostatic and magnetic energy is flowing internally and the more chakras and nadis are free and open, the stronger the reception of electromagnetic vibrations is. This vibration is also called the sound. Like the sound can not travel through the vacuum, so the vibrations can not flow through the blocked energy channels.
In Nada Yoga, as with all yoga paths, Yoga is the mean and the goal.

OM is the primordial sound. As recognized by the ancient Indian sages, it is the sound which could be experienced in every waterfall, in every movement of wind, in every cell.
OM is a mantra, the vibration of consciousness, or an instrument of the mind. MAN is the Sanskrit root for the word mind and TRA for the word liberation.
In the moment when we sing OM or other mantras we turn off our thoughts. This state leads us to a higher state of mind, Pratyahara, or withdrawal of the senses, a perfect stillness and the same time a perfect presence.
Since our spiritual birth in our being are stored impressions (Samskaras, not to be confused with Samsara, which is the wheel of death and rebirth), and chanting OM or other mantras, mentally or loudly can free us of those impressions, or it can help to process them.
People of a higher level of consciousness can hear their own heart chakra. These experiences are entirely authentic just like the entire Yoga Sadhana, the yoga practice.

In India Nada Yoga is much revered. In both the West and India it is used as a therapy.

Sanskrit is the language of the heart.

Nada itself is Anahata, the heart chakra, the seat of the cosmic sound.

Inner voices are not necessarily a sign of disease.

Nada Yoga is the union of the inner universe with the external, the internal sound with the external sound, the microcosm (human body) with the macrocosm (Brahmanda).

Nada Yoga, by listening to the inner sounds, leads to Laya Yoga.

LAYA YOGA

is a state of consciousness, the perfect peace of mind, which the aspirant archives spontaneously and after a long and dedicated practice of hatha yoga (which are not only pure physical exercises). When the energy channels and the energy centers are open, cleaned and united, then the ego can dissolve. The Sanskrit word laya means resolution. It is a Turiya, the sum of all three states of consciousness, the transcended state of the highest truth. It is the point on the OM sign.

RAJA YOGA

also known as the Yoga of Mind, Classic Yoga, Patanjali Yoga, Yoga of Meditation or, for informed people, Yoga.
Raja literally means King.

Patanjali, the great Indian sage whom is very little known about, has compiled the essence of Yoga in his Yoga Sutras which are the Yoga aphorisms. Their date is ranging from the 400 B.C. to the 400 A.D. and they were passed down oral from the teacher to the pupil. The Yoga Sutras are wonderful and profound wisdom on yoga and they form the basis for the Yogic tradition.
Yoga basically means unity and sutra means thread in a sense that it is something that keeps together.
Yoga Sutras compare our mind (citta) and its fluctuations (vrittis) with the waves on the surface of a lake, which are caused by external and internal factors. Our emotions, thoughts, impressions, memories (therefore the unconscious and subconscious mind) are the internal fluctuations or the seabed. Our senses, sight, smell, taste, touch and listening produce wind, or waves and are the external fluctuation.
Now, only when the water is still, therefore the conscious, one can see his true self, to realize his own soul and unit it with the spirit, higher reality, higher consciousness.
Patanjali begins his Yoga Sutras with the sutra:

“Yogash citta-vritti-nirodha”
which, depending on the individual or collective psychology, has been translated in several different ways. The meaning of the single words are these:
Yogasch- unity
Citta- mind
Vritti- whirl, fluctuations
Nirodha- mastered, governed, control.
Yoga is control of the fluctuations (internal as well as external) of the mind.

Raja Yoga is a long way and, as the name says, the aspirant (practitioner) is a king who has his own mind under control.
The material wealth of a king, or the person who, by his material possessions (or by his academic degree), feels like a king, in this case has no value. Raja Yogi or king can be anyone who is willing to bring a lot of effort, honesty and self-discipline in his daily life driven by challenge for change and transformation.

This path is also known as Ashtanga Yoga (this is not to be confused with the Hatha Yoga style that has been invented by Pattabhi Jois in Mysore, India).

Ashta means eight and Anga means limbs.