In the Mahayana and Vajrayana Buddhist traditions, there are two types of Bodhisattvas, the mortal and the celestial.

The mortal Bodhisattvas are beings who incarnate on earth, and have advanced spiritually to the point where they can enter nirvana and become Buddhas. Instead, they take a vow to refrain from entering Buddhahood in order to relieve the suffering of other beings, and spread the Dharma (Buddhist message). They dedicate their life on earth to compassionate action and usually choose to incarnate over and over again to fulfill their vow.

Maitreya is said to be such a Bodhisattva who will incarnate at some future time on earth.

The Dhyani Bodhisattvas are Bodhisattvas of the second type (celestial Bodhisattvas). Each Dhyani Bodhisattva is an emanation of one of the five Dhyani Buddhas. Such a Bodhisattva is created by his spiritual parent, the Dhyani Buddha, and is an active form of his creator who is capable of interacting in the psychic and physical worlds to relieve suffering. None of these celestial Bodhisattvas have ever been fully incarnate in a human body.