Pet trait is a personality system for pets in The Sims 4: Cats & Dogs. They are unique to them and are not available to Sims. On the other hand, traits for Sims are not available to pets either. Pet traits affect how cats and dogs perform, hunt and are interested towards Sims.
There is a total of 34 pet traits, 17 for cats and 17 for dogs. Some traits have unique attributes for one of the two species, but most traits are identical to one another. For example, the mischievous is a trait for cats and troublemaker is a trait for dogs, and both of them have the same general idea of the pet misbehaving. Pets created in Create a Pet can have up to three traits. Sims can get to know a pet before adopting it using the interaction "Get to know", learning one trait each time.