The Six Desire Heavens are also called the Heavens of the Desire Realm. The Desire Realm, Form Realm and Formless Realm are the Triple Realm. We are now encompassed in the Heaven of the Four Kings, one of the Six Desire Heavens.
The first heaven is the Heaven of the Four Kings. It is the heaven which we can see directly, ruled by four great heavenly kings. It is located halfway up Mount Sumeru. The lifespan of the gods there is five hundred years, with one day and night in that heaven equalling fifty years in the human realm.
The second heaven is the Trayastrimsha Heaven. Trayastrimsha is Sanskrit and translates as Heaven of the Thirty-three. What does this mean? Lord Shakra, who dwells in the center, is known as Indra in the Shurangama Mantra. He's known as God to the Catholics and Christians, as the Jade Emperor to the Chinese, and as the Lord on High in the Book of History. There are eight heavens to the east, west, south and north. Four times eight makes thirty-two heavens altogether.
The third heaven is the Suyama Heaven. Suyama is Sanskrit and means "time division." These gods are extremely happy all the time and sing songs from morning to night. What do they sing? "Merrily indeed! Merrily indeed! I'm tremendously happy!"
The fourth heaven is the Tushita Heaven. Tushita translates as joyful contentment. The beings there are delighted and satisfied at all times, free of worries and afflictions all day long. It's also called the "heaven of fulfillment" because the beings are satisfied and constantly happy, without cares or afflictions.
The fifth heaven is the Heaven of Delight by Transformation (Nirmanarati). These gods can transform happiness. The clothing and food they desire appear as soon as they think about them. Having mastered such transformations, they are extremely happy.
The sixth heaven is the Heaven of Self-mastery through the Transformation of Others' Pleasure. "Transformation of Others' Pleasure" means those beings don't have any joy of their own, so they usurp the happiness of other heavens. Why do they do this? Simply because they are unreasonable, like bandits in the world who rob others' money and possessions, not caring whether they live or die. Many demons and their retinues dwell in this heaven.
The gods in the Six Desire Heavens still have the three desires for food, lust and sleep, so they are still in the Desire Realm. Just as in this world, there are marriages between males and females. Although the heavens are blissful, after the gods' heavenly blessings are used up, they must still undergo transmigration.