In the Hindu Philosophy, the Yoga is one of the six orthodox philosophical schools, and The Yoga Sutras of Patajali, are the oldest Sanskrit texts foundational of Yoga.

These treaties are based on the doctrine Vedanta and in the Hindu sacred writing Bhagavad Gita, with aphorisms about philosophical aspects of the mind and the conscience, and the technique to unite the individual conscience with God; and although is a matter of a short text, the Yoga Sutras have had an enormous influence in the philosophy and practice of the yoga, just as relevant today, as when first written.

The Sanskrit word Yoga, is utilized in the work to be referred to a state on mind in which the thoughts and the feelings are in suspense (known as "Nirodha" in Sanskrit).

The word Sutra, signifies thread or to thread. This refers to the threads of the Japa mala, (Hindu prayer beads), upon which the aphorisms that sutras are strong like beads.

Although the Yoga Stra date between the century II before Christ and the century VI before Christ, not yet has been able to be determined clearly the identity of its author neither the exact date of its composition.

They are texts that do not appear like a unit but as different parts, even uneven inwardly each one of them, what reinforces the belief that they would be a matter of diverse sources of origin and compiled subsequently.

In to the year 300 a. C., the yogi Patajali, a Vedanta Hindu, compiled the yoga Sutras and classified them in the eight parts that are known since then, and therefore, often he is also named as the founder of the Yoga.

Mythological, Hindu people consider Patajali as an incarnation of the divine snake Adi Sesha who is another aspect of the God Sankarshana (the first expansion of the God Vishn), that surrounds and maintains the universe in the shape of a cosmic ocean.

The Yoga-Stra, are 195 aphorisms (stras), or short phrases formed with technical words and assembled under a very strict grammatical rules.

Each Sutra is the summary of a dialogue about the "Darshana Yoga", maintained between a teacher and their student. The summaries of this conversation constitutes the text "Yoga Sutra".

The book is divided into four chapters or books (Sanskrit "Pada"):

Samadhi Pada: With 51 aphorisms, is dedicated to the general nature of the yoga and its technique: "The complete internalization", its different forms, the obstacles and the media through which arrives at the cessation of all the mental processes, which is the meaning the yoga. It refers to a blissful state where the yogi is absorbed into the one. Is a matter of responding to the question: "What is the yoga?".
Sadhana Pada: "The practice". This section tries the conditions of the human life and try to respond to the question: "Why should we practice yoga?". All its impediments are exposed, their causes and their consequences; and finally, this section analyze the external media or the five first practices of the Classical yoga. It is comprised of 55 aphorisms.

Vibhuti Pada: (Sanskrit word for "power" or "manifestation"). Dedicated to "the exceptional faculties", with other 55 aphorisms (or 56, according to some versions) This chapter exposes the internal media that complete the external part of the yoga of the eight steps, and discusses in detail the "Siddhi" or extraordinary powers that challenge the laws of the science. Such powers are achieved involuntarily during the course of the practice.

Kaivalya Pada: (Means "isolation", but as used in the sutras stands for emancipation, liberation).This chapter refers to "the independence or transcendental isolation"; with only 34 aphorisms, they treat philosophical problems implied in the study and practice of the system; especially two fundamental questions of the metaphysics: the time and the nature of the knowledge. The Kaivalya Pada describes the nature of liberation and the reality of the transcendental self.

Patajali defines the yoga in his text as "the cessation of the fluctuations of the mind", and after developing a meticulous study of the operation of the human awareness, enumerates eight steps or stadiums called Ashtanga (the yoga of eight members) to reach that objective, and that the yogi should observe and to practice rigorously and in simultaneous. They are prescribed in the second Pada of the Yoga Sutras

- Yama: Universal ethical principles: not to lie, not to do damage, sexual abstention and renunciation.

- Niyama: Disciplines of individual conduct: Cleaning or neatness, satisfaction or acceptance of the personal reality, asceticism, study and devotion to the absolute thing.

- Pranayama: Breathing techniques. Beneficial to health, steadies the body and is highly conductive to the concentration of the mind.

- Pratyahara: Orientation of the senses toward the interior. Concentrating the mind in a single point, they look that the senses be set apart of the objects and the person be centered in if same.

- Dharana: Concentration: Focusing the mind in a single point to avoid the dispersion.

- Dhyana: Meditation: The act of meditation and the object of meditation remain distinct and separate.

- Samadhi: State upper of awareness: subject and object, both disappear in the same meditation.

This link gives us more information about The Yoga Sutras of Patanjali and a link to a translation of the Sutras.

And a link to get an audio CD with the Sutras:

With this web page we can ear each yoga sutra in audio MP3 format:

We can find many of books about yoga sutras of Patanjali in Amazon, with translations, commentaries, reflections, etc:

I found this page very interesting, about translation of the yoga sutras of Patanjali, but also included commentaries about the Sutras and Patanjali himself: