Patanjali has divided yoga into eight folds known as ashtanga yoga.
It is a common myth that yoga means yogasana. Actually aasana is just one part of yoga whose ultimate goal is to attain
Samadhi or Nirvana.
These are the eight constituent parts of the discipline of yoga. A person who desires of achieving the full goal on the path of yoga is supposed to
practice all these eight steps in sequence and it is postulated that one can not progress to the stage
ahead unless he has mastered the stage behind.
Vahiranga and Antaranga Yoga
Yama, Niyama, Aasana and Pranayama have been graded as
Vahiranga yoga or external yoga practices, while the further four steps, namely
Pratyahara, Dharana, Dhyana and Samadhi are considered as Antaranga yoga or internal yoga
practices.
