When the body is no more, you enter your imagination.
So the afterlife is like a lucid dream, but without "glitches" when the brain is involved, a smooth and stable lucid dream, a new boundless reality.
See it as a realistic solo offline rpg game, you can use cheats and mods there is no rule. And the npcs, despite not having a soul like you, (not being controlled by external entities that are the players, but entities born directly in the games code) And this life is an mmo, it's online so you play with other people like you that you cannot control, there are rules and anti cheat, and you are weak and vulnerable.
When you're tired of this solo rpg without limits, you can wish to erase your mind, it's the second death. You killed your body (you then left the physical plane), you killed your mind (you then left the mental plane), what remains now is your core, your True self, the indestructible thing in which all layers of reality are built on. Basically you return to THE ALL, it's an absolute state that absolutely cannot be described. But this state is not eternal as nothing is eternal and everything is cycling, so then the layers are built again and realities are formed.
Keep in mind these things are impossible to describe or explained in words, it's very simplified, planes of existence are more like a spectrum.