I'll give some basic explanations as they are subject to change.

So.

[b]Cash[/b] is money, currency, capital. You'll use this to recruit, buy zones, bribe, et cetera.
[b]Bodies[/b] is the amount of people who are loyal to your organization. Crime Families will have a slower growth, as their only members come from the bloodline.
[b]Zones[/b] is how many regions you control. Regions will offer a cash flow.

So with the SMPD, you're less of a single person and more of a representative entity. [b]Investigate[/b] will be an action where you pick a zone, and any activity that an organization is doing will be revealed. However, if they aren't doing anything, it'll just be a false lead.