What is Mormon Celestial heaven?

Answer 1

According to the Doctrine and Covenants, a book of canonized scripture which contains the revelations to Joseph Smith and subsequent prophets of the Church of Jesus Christ of Latter-day Saints (the "Mormon" church), heaven is divided into three kingdoms or degrees. The highest of these is the Celestial Kingdom. The Celestial Kingdom will contain those who have "received the testimony of Jesus" and been "made perfect through Jesus" (D&C 76) as well as all those "who have died without a knowledge of the gospel, who would have received it" (D&C 137) and "all children who die before they arrive at the years of accountability." (age 8) (D&C 137) Because of the high numbers of people who fall into the latter two categories, it is assumed that the Celestial Kingdom of heaven will by far be the most populated.
It is believed that in order to obtain the Celestial kingdom, one must have repented of their sins, received the ordinances of salvation (i.e. baptism and a temple endowment), and been faithful to the covenants they made in those ordinances. The "saving ordinances" may have been received during mortality or vicariously after death, and it is believed that all people, living and dead, will have the opportunity to accept these ordinances.

In the Celestial Kingdom, we will dwell as resurrected and glorified beings in the presence of God the Father and His Son Jesus Christ. Here we will have the opportunity of eternal progression - forever learning and gaining wisdom and power in the presence of God.