Difference between ray tracing and high global illumination

[Squished]

Wondering what the difference is. Settings for high GI and above enable ray tracing for more accurate lighting. But there's also a separate ray tracing option with choice of partial or full. What does this extra setting do in addition to the raytraced lumen?

[joridiculous]

(Kind of technical but its easy enough to understand)

Global Illumination is the process of lighting or illuminating a scene by calculating the light emitted by luminant sources on and off the screen (by approximations or tracing its path). With ray and path-tracing, the light rays are cast from these sources, reaching various objects in the scene and illuminating them.

Ray Traced Global Illumination (RTGI)
These indirect or diffuse rays act as newly cast rays, further crashing into other objects and illuminating them in the process, the object redirecting them now behaving as a light source. When the ray finally reaches the camera (the screen), the information gathered by it is used to calculate the lighting of the scene.

(From Unreal)
Lumen is Unreal Engine 5’s new Fully Dynamic Global Illumination and reflections system that is designed for next-generation consoles. Lumen is the default global illumination and reflections system in Unreal Engine 5. It renders diffuse interreflection with infinite bounces and indirect specular reflections in large, detailed environments at scales ranging from millimeters to kilometers.