The Buddhadharma—Buddha’s teaching—is expansive and all-embracing. It encompasses all the phenomena in the mundane, the transmundane, and the mundane as well as transmundane world. Yet, the essence and core of the Buddha’s teaching always rely on each sentient being’s own true mind—the eighth consciousness Tathagatagarbha—as their basis. Sentient beings experience suffering because they do not understand the meritorious virtues and wondrous functions of the true mind and crave and take the five aggregates as true existence instead; as a result, they have been performing assorted wholesome and unwholesome acts and are bound in the cycle of birth and death in the three realms for innumerable eons. In Buddha’s teaching, all sentient beings possess their own individual Buddha-nature—the inherent potential to achieve Buddhahood—but fail to realize that due to the attachment to their illusory thoughts. If they can practice and cultivate according to the Buddhadharma to subsequently attain realization, they will be able to gradually achieve Buddhahood. The Buddhadharma is and must be verifiable, not just based on theory. Otherwise, it would just be a collection of conjectures and speculations, which could only be classified as theory or hearsay. The Overview of the Three-vehicle Bodhi series will systematically introduce the content of the practice and cultivation of the Buddhadharma.