According to the teachings of the Mormon Church, "temple worthy" Mormons are "sealed" for "time and all eternity" in their temple ceremonies.
The purpose of the Mormon male is to "progress" to "godhood" -- i.e. "As man now is, god once was. As god now is, man may become." The Mormon man will "call forth" his wife (i.e. resurrect her) after death where she will serve as his "sacred vessel" eternally procreating "spirit babies." The wife will serve as one of many in a polygynous union with her husband and other wives.
Mormons do divorce, and Mormon widows and widowers do remarry. As a result, things get very complicated.
You can find out more about the Mormon faith from many excellent sources. I recommend you begin here.