In Buddhist philosophy, Buddha-nature is the potential for all sentient beings to become a Buddha or the fact that all beings already have a pure buddha-essence within. "Buddha-nature" is the common English translation for several related Mahayana Buddhist terms, most notably tathāgatagarbha and buddhadhātu, but also sugatagarbha, and buddhagarbha. Tathāgatagarbha can mean "the womb" or "embryo" (garbha) of the "thus-gone one" (tathāgata), and can also mean "containing a tathāgata". Buddhadhātu can mean "buddha-element," "buddha-realm" or "buddha-substrate".
The moon hidden by the clouds is a metaphor for Buddha-nature which is always shining but can be hidden or covered over by the afflictions.
The Tathāgatagarbha Sūtra states that the tathāgatagarbha is like the grain of rice contained inside of the husk of the rice plant
The Tathāgatagarbha Sūtra uses the image of a Buddha within a lotus flower as a metaphor for the tathāgatagarbha
A ritual vajra, a symbol of indestructibility, which is used in the Ratnagotravibhāga as an image of the adamantine-like permanence of buddha nature.
The Ratnagotravibhāga and its vyākhyā commentary, is an influential Mahāyāna Buddhist treatise on buddha-nature. The text is also known as the Mahāyānottaratantraśāstra. The RGVV was originally composed in Sanskrit, likely between the middle of the third century and no later than 433 CE. The text and its commentary are also preserved in Tibetan and Chinese translations.
A common simile for buddha nature is the sun, which always shines even when it is obscured by clouds.
Lotsawa Marpa Chokyi Lodro, (1012-1097), a student of Maitripa.