Tathāgatagarbha, or the "embryo of Buddhahood," is a central concept in the Buddha-nature philosophy. It is often used interchangeably with the term Buddha-nature, but there are subtle differences between the two.

Buddha-nature refers to the inherent potential for enlightenment that exists within all beings. It is seen as a natural and essential aspect of our being, rather than something that is acquired or achieved. This concept is rooted in the Mahayana teachings of emptiness, which states that all phenomena lack inherent existence and are therefore empty of any fixed identity. Buddha-nature is seen as the true nature of reality, and the ultimate goal of Buddhist practice is to realize this nature and attain enlightenment.

On the other hand, Tathāgatagarbha specifically refers to the potential for enlightenment within sentient beings. It is often described as a seed or embryo that has the potential to grow into a fully enlightened being. This concept is closely related to the teachings of the Lotus Sutra, which states that all beings have the potential to become Buddhas. Tathāgatagarbha is also associated with the concept of the "one vehicle" in Mahayana Buddhism, which teaches that all beings have the same potential for enlightenment regardless of their individual differences.

One way to understand the relationship between Tathāgatagarbha and Buddha-nature is to see Tathāgatagarbha as the potential and Buddha-nature as the actualization of that potential. In other words, Tathāgatagarbha is the seed and Buddha-nature is the flower that grows from it. This understanding highlights the dynamic nature of the concept of Buddha-nature, as it is not a fixed or static state but rather a continuous process of growth and development.

Another way to understand the relationship between the two is to see Tathāgatagarbha as the underlying reality of Buddha-nature. Just as all phenomena are empty of inherent existence, Tathāgatagarbha is seen as the ultimate reality that underlies all beings and their potential for enlightenment. This understanding emphasizes the interconnectedness and interdependence of all beings, as they all share the same fundamental nature.

In conclusion, Tathāgatagarbha and Buddha-nature are intimately related concepts in the Buddha-nature philosophy. While Buddha-nature refers to the inherent potential for enlightenment within all beings, Tathāgatagarbha specifically refers to this potential within sentient beings. Together, they highlight the dynamic and interconnected nature of reality and the potential for all beings to attain enlightenment.