Traits and mutations are alterations to a beb's body that makes them unique! Traits can be represented in lots of different ways, even across a single trait! It's up to the designer how that trait fits into its description to some degree!
Traits come in 4 rarities; Uncommon, Rare, Ultra Rare, and Legendary
Mutations come in 2 varieties; Minor and Major
If you want more examples of how a trait can vary, you can search for that trait in the Beastiary to see Bebs that have that trait!