Short answers, pulled from the story.
Heaven is a religious cosmological or supernatural place where beings such as deities, angels, souls, saints, or venerated ancestors are said to originate, be enthroned, or reside. It is often described as the highest place, the holiest place, or a paradise, set in contrast to Hell or the Underworld.
The modern English word heaven comes from Middle English heven, attested in 1159, which developed from the Old English form heofon. By about 1000, heofon referred to the Christianized place where God dwells, but originally it meant sky or firmament, as in Beowulf around 725.
The ancient Mesopotamians regarded the sky as a series of domes, usually three but sometimes seven, each made of a different precious stone. The lowest was jasper and held the stars, the middle was saggilmut stone and housed the Igigi, and the highest was luludanitu stone personified as An, the god of the sky.
In Islam the afterlife destination of the righteous is Jannah, the Garden, often translated as paradise. The Qur'an and Hadith also describe seven samawat, or heavens, and give Jannah several names including Al-Firdaws, Daru-s-Salam the Abode of Peace, and Jannatu-l-Khuld the Garden of Immortality.
In Buddhism the deva realms or heavens are still part of samsara, so beings eventually use up their good karma and are reborn, making the real goal nirvana beyond the heavens. In Hinduism heaven is ephemeral and tied to the cycle of birth and death, and the wheel is broken only by self-realization, which is Moksha and final communion with Brahman.
Traditional Christianity teaches that Heaven holds the throne of God and the holy angels, and is the abode of the redeemed dead, often as a temporary stage before the resurrection and return to the New Earth. Pope John Paul II described it as neither an abstraction nor a physical place in the clouds, but a living, personal relationship with the Holy Trinity.
Yes, many cultures pictured a layered Heaven. The Nahua peoples built thirteen levels topped by Omeyocan, Gnostic texts describe seven heavens under the Archons with an eighth above, the Qur'an speaks of seven samawat, and Maori versions number the heavens from as few as two to as many as fourteen.