I thought I’d start with beginnings, since they affect so much else.
Mormons reject the classic (and largely post-Nicene) Christian concept of creatio ex nihilo, that is, creation out of nothing, in at least two important senses: the existence of individuals and the ultimate framework for our current space-time continuum. Let’s focus on the first for now.
We believe that some essential nature of our personal being is eternal, indeed co-eternal with God. The arc of individual existence, in current Mormon terminology, goes like this:
intelligence: nowadays, this term is used to describe our core eternal being, the part of us that has always existed. This is generally considered to be individualistic — that is, you and I have always existed as separate entities — though a few within the Church have argued for more of a ‘raw bulk material’ concept (with possible recycling). Joseph Smith’s statement (in the King Follett discourse) was that “…God never did have power to create the spirit of man at all. God himself could not create himself: intelligence exists upon a self existent principle…”.
pre-mortal) spirit: at some point prior to this life, God encased our intelligences in ‘spirit bodies’ (and thus became “the Father of spirits“). We know nothing about the process and we frankly know very little about the conditions there, though this doesn’t stop Mormons from rampant speculation and presumption, plus generating a fair amount of folk doctrine. 🙂 It also should be noted that early LDS scripture and discourses on this subject did not make as clear a distinction between the terms ‘intelligence’ and ‘spirit as is currently made in the LDS Church today (cf. the King Follett discourse above, as well as this passage from the Book of Abraham).
mortal being: we are born into this life with an impermanent bond between our spirit body and our physical body — in other words, we’re mortal and will die (breaking that bond).
(post-mortal) spirit: after death, we exist again as spirits for a period until we are resurrected.
resurrected being: resurrection permanently fuses our spirits with an immortal physical body.