103-form Yang family tai chi, also called the Traditional Form (or, Long Form), is a prescribed sequence of moves used to practice Yang-style tai chi.
They are usually performed slowly and are designed to string together an inventory of important techniques, and to promote relaxation, as well as other foundational principles.
This sequence of moves, when performed at its prescribed speed, usually takes approximately 25 to 30 minutes to complete.
The following is an English translation from Chinese of the form list used by the current Yang family teachers.
The book called Yang Shi Taijiquan ("Yang-style tai chi"), by Fu Zhongwen, breaks the form into each of its discrete movements.