Topic category: User side tutorials
This topic is only to help you with the Creature Type, when you create a mob.
Undead : It's all mob like Zombies and Skeletons.
Arthropod : Those are spiders and cave spiders.
Illager : Those are illagers, like Vindicator, and Illusionist.
Undeafined : It is all other mobs of Minecraft.
Hoping that this tutorial/topic helped you.