Starfield Skills -> Social Skills
Theft is a skill in Starfield located in the Social Skill tree that improves your chances of successfully pickpocketing NPCs.
Theft Skill Description
While not entirely honorable, and certainly not legal, it is nonetheless occasionally necessary to discreetly remove property from someone’s person.

Theft Skill Ranks
Rank 1
Unlock the ability to pickpocket targets.
Rank 2
10% greater chance to successfully pickpocket.
Rank 3
30% greater chance to successfully pickpocket.
Rank 4
50% greater chance to successfully pickpocket. Can now pickpocket holstered weapons.