In Buddhism, we borrowed the word heaven to describe planes of existence that is higher than humans. They are considered higher planes of existence because the degree of sufferings is lesser than the human realm.
The Buddha taught that beings over there have a limited lifespan too and these heavens arises from causes and conditions. However, the lifespan of these beings is so long that some of them may mistaken their life and their world to be infinite.
The following is a summary, referenced from, https://en.wikipedia.org/wiki/Buddhist_cosmology_of_the_Theravada_school
The heavens are sub-divided into 3 categories. Within each category are numerous levels of heavens.
The Sense-Sphere realm
There are 4 levels of heavens under the formless realms.
- The beings here do not have a material form and only their mind is present.
- They are reborn here because of their level of mental development.
- Unfortunately, they do not interact with external factors and thus, do not have opportunity to hear dharma.
- Usually, they will be reborn to lower realms once their life span is exhausted.
The highest level is known as Sphere of Neither Perception Nor Non-Perception. This mental state was taught by Ascetic Siddhartha’s 2nd meditation teacher (note: before Prince Siddhartha started to use his own method of mind training, he seeked out the best teacher of his time). Ascetic Siddhartha also attained the same level of mental development as his teacher. He then realised that this is not true enlightenment and beings born here are still stuck in Samsara.
Buddhist learn this lesson as beginner so that we do not mistaken this type of mental achievement as Enlightenment during our meditation.
Next is the Sphere of Nothingness.This mental state was taught by Ascetic Siddhartha’s 1st meditation teacher. Likewise, when Siddhartha achieved the same state, he realised that it is not Enlightenment and beings are still trapped in Samsara.
If we read the biography of Buddha, He started his spiritual career by learning from the best meditation masters of his time. Having achieved the same level of mental development of his teachers, he discovered that they are not true enlightenment. For beginners embarking on mind training, it is important to keep this story in mind and not mistaken formless mental state as Enlightenment.
The other 2 planes of formless realm are The Sphere of Infinite Consciousness and Sphere of Infinite Space.
Note: People practicing mental development or training for higher spiritual “consciousness” would benefit from some understanding of the various realms of heavenly realms. From a Buddhist perspective, this is to prevent mistaking them for Enlightenment. (Best is to have a qualified spiritual mentor to check with)
Down from the formless heavens are the Fine-material heavens.
There are 17 levels (broad classification) of heavens under this category.
- A form is present.
- They are genderless.
- They are not exposed to extremes of pleasure and pain,
- They are not tied down by desires for sensual pleasures.
Within this classification is the Pure abode (Special Buddhist heavens)
Beings reborn here is sure to end up gaining enlightenment (escape from Samsara) It’s like a prep-school resting place before you break free! So this is where some Buddhist aim to be. It is an exclusive “club” and does not house beings who have acquire ordinary merit or meditative attainments. These heavens are free from the cycle of ultimate destructions. (In Buddhist cosmology, the apocalypse of world systems destroy some of the heavenly realms too)
However, Bodhisattva does not reborn here. This is because a Bodhisattva needs to return to Samsara to help liberate other beings. Whereas beings in these heavens do not return to Samsara but move on towards Enlightenment.
To be reborn here, you need to reach the stage of Anāgāmins (“Non-returners”) That means you need to have already removed the following fetters:
- Sakkāya-diṭṭhi: Belief in atmān or self (Buddhist wisdom)
- Sīlabbata-parāmāsa: Attachment to rites and rituals
- Vicikicchā: Skeptical doubt
- Kāma-rāga: Sensuous craving
- Byāpāda: ill will 
Note: Do not mistaken mere knowledge as realisation.
One of the famous inhabitant here is Brahma Sahampati. “He” is the one who implored Buddha to teach the Dharma. All the beings here are Buddhist and thus automatically they also protect Buddhist. Buddha had taught many ancient Gods and help them reached this state too.
There are five levels of heavens under this category of Pure abode.
- Peerless Devas (Akanittha deva):
- Clear-Sighted Devas (Sudassi deva)
- Beautiful Devas (Sudassa deva)
- Untroubled Devas (Atappa deva)
- Devas not Falling Away (Aviha deva):
Note: Deva means beings of higher realms. For English equivalent, sometimes people borrow the word God, angels, deities.
So up till here, we explained about the heavens that are exclusive to Buddhist; where all beings here are Buddhist.
Still within the broad category of Fine-Material World are other planes of heavens. Some of its inhabitants maybe Buddhist. However, they have not reached the stage of Anagamis. (unlike the beings in Pure abode)
Next down is the Bṛhatphala Planes. The beings here possesses a tranquil mental state of the 4th level of meditative absorption. When their life span is exhausted, they fall to a lower realm.
Next is the Śubhakṛtsna Planes. The beings here possesses a mental state of the 3rd level of meditative absorption. When their life span is exhausted, they fall to a lower realm.
Next down is the Ābhāsvara Planes. The beings here possesses a mental state of the 2nd level of meditative absorption. When their life span is exhausted, they fall to a lower realm.
The heavens narrated above are attained by people who trained in meditation to achieve deep meditative absorption. (Note: meditation is not unique to Buddhism) Some meditators mistaken these blissful mental state to be enlightenment. A Buddhist have to be careful and note that, meditative trance alone is not salvation. If you compare with the requirements for rebirth in the Pure abodes, you’ll easily see what is missing here.
Next down is the Brahma realm. The beings here possesses mental state that is equivalent to the 1st stage of meditative absorption. When their life span is exhausted, they usually fall to a lower realm.
To be reborn here, one either attained the 1st meditative absorption or practice meditation on loving kindness, compassion, altruistic joy, and equanimity. Beings here may mistaken their life span and world to be immortal.
One of the famous inhabitant here is the Great Brahma, due to his delusion he mistakenly believed that he was infinitely existing and he was the creator of everything. The story is narrated in one of the scriptures where Buddha went to Brahma realm to correct this misconception. The Great Brahma had an entire retinue of Brahma submitting themselves to his rule. (That is another story to be told later)
Up till here we described the various heavens under the category of Fine Material worlds. As a recap, the beings in Fine Material worlds have a form but the matter of their body is very subtle.
After the heavens of Fine Form is the heavens of Sense-Sphere.
The beings here enjoy sensual pleasure and enjoy certain powers. It’s the typical idea of heavens that most people have.
However, the lifespan is not infinite. Anyone can be reborn here as long as they lead a wholesome life and have wholesome karma. The human can invoke the help of the beings here and the beings here may be inclined to help too.
Buddhist typically “invite” these beings to attend their spiritual practice like chanting session, meditation session etc. The devas rejoicing such meritorious deeds also gain merits for themselves. In return the devas protect and support the Buddhist by encouraging and supporting their wholesome conducts and lifestyle. (It’s like a win-win arrangement)
Within the Sense Sphere heavens, are various heavens and they are classified as higher and lower heavens.
The highest level is the heaven of Devas Wielding Power over the Creation of Others (Parinimmita-vasavattin deva): Due to their glory, other devas serve and pleases them. Mara, the personification of delusion and desire, lives here. He tries his best to keep all beings within the grip of sensual pleasures. He is infamous for trying to prevent the Buddha from gaining enlightenment.
Next down is the heavens of Devas Delighting in Creation. The beings here create things for their enjoyment.
Next down is the heavens of contented devas. Also popularly known as Tusita heavens. Many bodhisattvas resides here. It is believed that Maitreya Bodhisattva is residing here now. Sakyamuni Buddha was residing here before he was reborn as Prince Siddhartha. There are Buddhist and non Buddhist inhabitants.
Next down is the Yama heavens
The above are higher heavens within the Sense-sphere heavens.
The lower heavens are occupied by beings with higher degree of attachment to sensual pleasures. Although enjoying life in general, they are also afflicted by strife and fighting. It is said that the Asuras (fallen angels) are constantly trying to re-occupy this heaven by waging war against it.
Foremost is the popular heaven of 33 gods (Tavatimsa deva).
The Chief here is Sakra, a Buddhist. His godly virtues are righteousness, patience towards aggressors, and compassionate treatment of wrongdoers.
Next down and the lowest level heaven is the heaven of the 4 heavenly kings. The 4 heavenly kings are considered guardians and each have their own retinue of celestial / supernatural armies.They report to Sakra and they are the front line defense against the Asuras (Fallen angels)
Above describe the various heavens as recorded in Buddhist scriptures.
Hope you enjoy reading.
May all be well and happy.