MaterialQualityLevel can set to high medium and low, what is the difference in rendering?

MaterialQualityLevel can set to high medium and low, what is the difference in rendering?

MaterialQualityLevel controls Quality Switches, that you can use to create variations of the same material for different quality levels.

Thank you!
yes i know it useful for Quality Switches, and is there some engine difference in rendering? such as using diffent shader to comput lighting?

No, no difference besides Quality Switches.

thank you!