Ashtanga Yoga is a style of yoga that goes back to Krishnamacharya in the late 1800's in India. This form of yoga went worldwide primarily through his student, Pattabhi Jois as well as those who later learned from Jois.
If you have done yoga, you have likely practiced sun salutations. Sun salutes are the beginning of every ashtanga yoga practice and have been adopted as a great warm up by many other styles of yoga. Ashtanga yoga also includes other specific sets of postures that are repeated in the same order every class. Every class begins with Sun Salutations and ends the same Finishing Postures and can have either the Primary Series or the Intermediate series and/or Advanced A or B in the middle. In addition to the postures, ashtanga yoga places a large emphasis on the breath and the internal locks, or bandhas.
If you are interested in learning these series of postures go to ashtangayogi.com to the "Complete Ashtanga Yoga Syllabus" link on the home page. There you will find images of every posture in order. Enjoy!