Executive order = federal level. He did that because states weren't prosecuting and there needs to be a mechanism to charge people (if it didn't already exist). Basically that means by default 85%. Prison terms simply don't last to the max time charged no matter what but Fed time is always harsher even if Fed prisons are supposed to be more lax. A state charge is when the state brings charges on you. This is like 75% of crimes. Federal is typically when you violate federal property, cross state lines, or run into some kind of special law that is enforced at a federal level. Transporting drugs across state lines is one example. Weed may be legal in one state, not legal in another. Getting caught in the latter state with the drugs and provable have departed the previous state you could end up charged at a state level for the possession but at a federal for the transporting across state lines maybe.

IANAL though and probably not totally correct.