In the API Name of Document Types, Objects, Fields, Lifecycles, and so on, there are three suffixes __V, __VS and __C. What is the difference between them?
The __vs (Veeva Systems) suffix indicates that the properties are system generated items.
The __v (Veeva) suffix represents a shortened, more recent version of the once widely used __vs extension.
Items labeled __vs and __v both are system generated, with the only differentiation between the two is the age in Vaults that use either naming convention more often.
The __c (Custom) suffix stands for the custom items such as Document Fields / Types / Lifecycles / Objects that are created by users.
Vault Help Documentation: About Document Field Administration