Level 1, House-Safe: if a creature is deemed House-Safe it is safe to keep in your home even if it untrained, they are commonly herbivores with few exceptions and even then, they don't hunt for the meat they consume

Level 2, Trainable: if a creature is deemed Trainable, they are usually herbivories, however about 20% of Trainable level creatures are omnivores, they are unlikely to harm a human unless they feel threatened or are starving

Level 3, Illegal: if a creature is deemed Illegal, it is the same as Trainable level, however they have certain features and emit certain chemicals that may make you commit a crime or put you in a state similar to being under the influence

Level 4, Dangerous but discernible: if a creature is deemed Dangerous but discernible it is a carnivore, if you see one in the wild, follow the instructions in the respective article

Level 5, Dangerous and humanoid: if a creature is deemed Dangerous and humanoid, it is practically the same as a Dangerous but discernible monster but it is more dangerous as it can do more

Level 6, Looks Human: you will not be able to discern it until it is too late.