What is packed brown sugar? What section of the store do I find it in?
Oh dear heart, the cookbook writers of the world are trying to run you ragged. Packed brown sugar, unlike light or dark brown sugar, is not a type of brown sugar, but a
reference to how you measure it. It means that rather than lightly spooning the brown sugar into a measuring cup and leaving lots of air pockets, you pack it into the measuring cup and squish it down until you can't fit any more in.
That doesn't answer the question of whether you should use light or dark brown sugar. Often the recipe specifies, but if it doesn't, generally you use light brown sugar. If you prefer the more robust flavor of dark brown sugar, though, you can certainly use it instead.
And we're giving serious thought to knocking your self-proclaimed cooking rank down a notch from "advanced beginner" to "novice." Don't think of it as a demotion; think of it as an opportunity to grow.
Softening Rock-Solid Brown Sugar
Using Granulated Brown Sugar
Substitute for Brown Sugar
How to Find (Make) Liquid Brown Sugar