From Destinypedia, the Destiny wiki
Intrinsic traits, also simply called intrinsics, are special perks always found on a given weapon that defines its basic behavior in Destiny 2.
An intrinsic trait is, as the name suggests, an inherent part of a weapon and cannot be swapped out. Different intrinsic traits define the archetype of a weapon, which includes base impact and rate of fire, and are useful in determining what weapon is best for a given playstyle at a glance.
List of intrinsic traits
Bows have their own specific set of intrinsic traits.
Swords have their own specific set of intrinsic traits.
Glaives feature a unique intrinsic trait.
These intrinsic traits are unique to a certain weapon or selection of weapons outside of the weapon class-specific trait.