The Yogasutras are ascribed to Patanjali, and they are the basis of his Ashtanga Yoga. Since the 12th century they were nearly forgotten in India, and texts like Bhagavad Gita, Yoga Vasistha and Yoga Yajnavalkya predominated.
In the 20th century the yogasutras experienced a revival. Patañjali divided his Yoga Sutras into four chapters (Sanskrit pada), containing in all 196 aphorisms, as follows:
Samadhi Pada (51 sutras). Samadhi refers to a blissful state where the yogi is absorbed into the One(Ishvara). Samadhi is the main technique the yogin learns by which to dive into the depths of the mind to achieve Kaivalya.
Patanjali describes yoga and then the nature and the means of attaining samādhi. This chapter contains the famous definitional verse: "Yogaś citta-vritti-nirodhaḥ" ("Yoga is the restraint of mental modifications").
Sadhana Pada (55 sutras). Sadhana is the Sanskrit word for "practice" or "discipline". Here Patanjali outlines two forms of Yoga: Kriya Yoga (Action Yoga) and Ashtanga Yoga.
Kriya Yoga is closely related to Karma Yoga, which is also expounded in Chapter 3 of the Bhagavad Gita, where Arjuna is encouraged by Krishna to act without attachment to the results or fruit of action and activity. It is the yoga of selfless action and service.
Ashtanga Yoga describes the eight limbs that together constitute Rāja Yoga.
Vibhuti Pada (56 sutras). Vibhuti is the Sanskrit word for "power" or "manifestation". 'Supra-normal powers' (Sanskrit: siddhi) are acquired by the practice of yoga.
But Patanjali warns : The temptation of such powers should be avoided, and the attention should be fixed only on liberation(Moksha). The purpose of using samadhi is not to gain siddhis but to achieve Kaivalya.
Siddhis are but distractions from Kaivalaya and are to be discouraged. Siddhis are but maya, or illusion.
Kaivalya Pada(34 sutras). Kaivalya literally means "isolation", but as used in the Sutras stands for emancipation or liberation and is used interchangeably with moksha (liberation), which is the goal of yoga.
The Kaivalya Pada describes the process of liberation and the reality of the transcendental ego.