Cosmogony, also called cosmogeny, is a branch of cosmology that deals with the origin of the cosmos, Universe, Solar system, or Earth. It is not to be confused with cosmology, as cosmology deals with the cosmos as a whole, including its origins.
Like how a cosmological model (or "Tier") is model that details the structure of the cosmos or reality, a cosmogonal model is a model that details the origin of the cosmos. Examples of such models include the Big Bang, the Inflation model and the model of a steady state universe.