The afterlife is a term referring to the continual existence of the mind or soul after the death of the body.
Some Humans believed that depend on ones actions during life they could go to different afterlives, the worthy would be ascended to heaven while the rest would fall into the depths of hell. (TOS: "Space Seed")
Religious Cardassians believed that after death, those who sought Oralius would "walk with her" in death. They believed that they would be reunited with those they had lost in life, and that before that point, the spirits of the dead--while not prayed to--did watch over the living. The alternate Skrain Dukat had at least two visions of this state, including the one he experienced as he was dying.(Star Trek: Sigils and Unions--"Sacrifice") The fate of those who refused Oralius' spirit was described as the "Eternal Tundra," and in Cardassians of the technological era, often equated with the forces of entropy and absolute zero. (Star Trek: Sigils and Unions--"Sacrifice")