For a follower of the Hinayana or Mahayana paths, there are the sutras and the shastras. The sutras contain the direct teachings of Buddha Shakyamuni, whereas the shastras are commentaries composed later by a disciple of the Buddha, such as Nagarjuna. Moreover, there are instructions on how to practice. For instance, many chapters of Shantideva’s Way of the Bodhisattva contain very clear instructions.
Studying the dharma can be compared to learning how to drive. There is a driving manual that explains what things are, how they work, the rules of the road and so on. Similarly, the sutras and shastras contain the basic knowledge you need in order to practice the dharma. When you actually learn how to drive, you receive personalized instructions based on your individual skills, your driving teacher’s style and the various practical situations you encounter. These are not necessarily presented in the same order as the information in the manual. Instructions can come in most unexpected ways.
In Vajrayana, there are the tantras as well as the pith instructions. For centuries, dharma practitioners have studied the tantras while practicing according to the pith instructions. Some students place great emphasis on the tantras, the actual texts which contain the theory of the view. Those who are intellectually or academically oriented can get quite caught up in explanations and theories. Other students who are more emotionally oriented tend to get caught up in the instructions. This was a common fault in the past and continues to be so today.