Skills are arranged into groups. A skill can belong to one or more groups. Groups simply provide a way to organise and list skills, though may sometimes be used as prerequisites for techniques.
Criminal: Skills used by criminals.
Military: Non-combat military skills. Often skills taught in modern armies.
Legal: Legal skills, Law, Business type etc.
Investigation: Detective and police skills.
Combat: Combat related skills, such as melee, brawl, pistol, rifle etc.
Firearms: Gun related skills.
Academic: Modern knowledges, often sciences, medicine, law and philosophies.
Lore: Ancient knowledges, mostly those pre-dating the Enlightenment.
Business: Business and monetary related skills.
Occult: Weird stuff to do with the supernatural.
Technical: Academic skills with a practical leaning, such as computing and engineering.
Vehicle: Driving, piloting, fixing vehicles.