The format of the stencil data that you can encapsulate within a RenderTexture.
Specifying this property creates a stencil element for the RenderTexture and sets its format.
This allows for stencil data to be bound as a Texture to all shader types for the platforms that support it.
This property does not specify the format of the stencil buffer, which is constrained by the depth buffer format specified in RenderTexture.depth.
Currently, most platforms only support R8_UInt (DirectX11, DirectX12), while PS4 also supports R8_UNorm.
Additional resources: GraphicsFormat, RenderTexture.depth.