Prefab variants are variations of a prefab that are saved as a separate prefab asset. They share their data with the original prefab asset but have a few overridden properties that differ from the original prefab.
For example, you can create a variant of a character but with different colors. The variant will then share the same character data, properties, and components. And if you update the original character, then the character variant will be updated as well. Except for the color, that property will be unique for the variant.
Right-click on a prefab asset and choose ‘Create > Prefab Variant’ to create a new prefab variant of that prefab.
Prefab variants automatically override all modified properties and save them to the prefab variant asset instead of applying them to the original prefab.
All the data of your prefab variant is still stored in the original prefab asset. The prefab variant only stores the values of properties, components, or objects that have been overridden.
If you want to make a modification that affects all prefabs, nested prefabs, and prefab variants of that prefab then you should modify the original prefab asset. If you only want to modify this prefab variant, then you should edit this prefab variant directly.
Prefab variants should be edited like normal prefabs by opening them in ‘prefab mode’. By default, all modified properties are saved as overridden properties. But, if you want, you can apply the modified properties to the original prefab.
To apply the values to the original prefab, click the ‘Overrides’ button in the Inspector. Then, click ‘Apply All’ to apply the values to the original prefab and no longer override them.