Angel

When a person dies in the Dragon Ball universe, their soul travels to Other World and stands before King Yemma for judgment. Most souls are sent to either Heaven or Hell and lose their physical bodies in the process. However, exceptional individuals, typically powerful warriors or those who performed great deeds in life, may be allowed to keep their bodies. These individuals are marked with a halo, the visual indicator that they are dead but physically present in Other World.

Training and Combat in the Afterlife

Goku is the most prominent example. After sacrificing himself during the Cell Games, he spent seven years training in Other World under the guidance of Grand Kai and alongside fighters like Pikkon. During this time he pushed his abilities far beyond what he had achieved while alive, eventually developing Super Saiyan 3. The afterlife proved to be an ideal training ground because the physical constraints of a living body did not apply in the same way, allowing Goku to push past limits that would have been dangerous or impossible otherwise.

Vegeta also retained his body during the Buu Saga through special arrangement, and Frieza famously spent his time in Hell wrapped in a cocoon, forced to endure a cheerful fairy paradise as punishment. The state does not inherently grant any power boost; it simply preserves the individual as they were at the time of death, plus whatever training they manage to accomplish in the afterlife.