This parameter controls spawning type for the biomes where his mob is defined to spawn in.

* A mob marked as Monster will only spawn in the dark or at night.
* A mob marked as Creature will spawn under direct sunlight on grass material blocks only. Do not use this spawn type with
mob type living entities as they will not spawn
* A mob marked as Ambient will spawn under any conditions except if block type prevents it,
but this category should be used for mobs with no gameplay effect such as bats
* WaterCreature will spawn in water, but with no other limitations

Spawn type system is in-depth explained [here](https://mcreator.net/wiki/mob-spawning-parameters)