Its primary subject matter is the monastic rules of conduct for monks and nuns of the Sangha.
The Buddha called his teaching the "Dhamma-Vinaya", emphasizing both the philosophical teachings of Buddhism as well as the training in virtue that embodies that philosophy. Shortly before his passing, the Buddha clarified to his disciples through Ānanda:
Now, Ānanda, if it occurs to any of you—"The teaching has lost its arbitrator; we are without a Teacher"—do not view it in that way. Whatever Dhamma and Vinaya I have pointed out and formulated for you, that will be your Teacher when I am gone.