The SunRaysEffect renders a halo of light around sun. The halo is shaped/blocked by world objects between the Workspace.CurrentCamera and the sun.
Like other post-processing effects, SunRaysEffect will only work while Enabled and when parented to Lighting or Workspace.CurrentCamera. Also, it may not render on low-end devices, and it may render differently depending on your Studio settings (see the Quality Level settings in Rendering → Performance).
For more details on this effect and others, see Post-Processing Effects.
Intensity determines the opacity of the sun rays. Values closer to 0 are less visible, while values closer to 1 become more visible.
Spread determines how wide the sun rays will spread across the sky. Its value should be set between 0 and 1 as values outside that range have undefined behavior.