Tushita

Tuṣita (Sanskrit) or Tusita (Pāli) is one of the six deva-worlds of the Kāmadhātu, located between the Yāma heaven and the Nirmāṇarati heaven. Like the other heavens, Tuṣita is said to be reachable through meditation. It is the heaven where the Bodhisattva Śvetaketu (Pāli: Setaketu, "White Banner") resided before being reborn on Earth as Gautama, the historical Buddha; it is, likewise, the heaven where the Bodhisattva Nātha ("Protector") currently resides, who will later be born as the next Buddha, Maitreya.
Descriptions

Like all heaven realms in Buddhism, the Tuṣita Heaven is the residence of divine beings or devas. According to an excerpt of the Pali Canon, a Theravada Buddhist text, time runs much differently than on Earth:
“ "That which among men is four hundred years, Visakha, is one night and day of the Tusita devas, their month has thirty of those days, their year twelve of those months; the lifespan of the Tusita devas is four thousand of those heavenly years..." ”
Mahayana View

In Mahayana Buddhist thought, the Tuṣita Heaven is where all Bodhisattvas destined to reach full enlightenment in their next life dwell for a time. One such reference can be found in the Larger Sutra of Immeasurable Life, a Mahayana text:
“ Each of these bodhisattvas, following the virtues of the Mahasattva Samantabhadra, is endowed with the immeasurable practices and vows of the Bodhisattva Path, and firmly dwells in all the meritorious deeds. He freely travels in all the ten quarters and employs skillful means of emancipation. He enters the treasury of the Dharma of the Buddhas, and reaches the Other Shore. Throughout the innumerable worlds he attains Enlightenment.

First, dwelling in the Tushita Heaven, he proclaims the true Dharma. Having left the heavenly palace, he descends into his mother's womb.
”

The Tuṣhita heaven is therefore closely associated with Maitreya, and many Buddhists vow to be reborn there so that they can hear the teachings of the Bodhisattva and ultimately be reborn with him when he becomes a Buddha. Other Bodhisattvas dwell in this heaven realm from time to time. Tuṣita is part of the same world-system as Earth, and so is relatively close, whereas the Pure Land of Amitabha Buddha is treated as a separate world-system entirely.