Should I Use Diamond or Whetstone? (Total beginner)

Hey everyone, new to the knife sharpening realm and just bought my first whetstone this week. I am a little confused by why some people use diamond over whetstone and vice versa? Is it due to the steel of the knife? Does having a western knife like a Zwilling reap better results on a whetstone because it is softer? Do Japanese knives do better on Diamond because the are harder? Or vice versa? What are the benefits to both types of sharpening approaches? Just trying to understand more in this rabbit hole of sharpening, TIA.