Template:Influence Stat Overview
Influence is a standard Background bought with Background dots, Freebies, and Starting XP.
Each dot of Influence belongs to a Sphere. A sphere is an overarching influence archetype, like "Police" or "Law". There is a standard list of Spheres.
Each Sphere has Specialties. A specialty is a sub-set of that sphere. For example, Criminal influence is a Sphere, like "Drug Trafficking" is a Specialty. The list of specialties is standard and pre-defined.
Lastly, when you pick influence Specialties, you pick a Niche. This is a free-form description of the sorts of people that your character's network is composed of. Someone who takes 'Drug Trafficking' might pick a particular gang, for example, or even just a particular drug.
When allocating dots of Influence, you can invest all of your dots into one Influence type or you can diversify (like 2 dots in Drug Trafficking, 2 dots in Arms Trafficking).