yup, that's basically it =)

if you have a cell that is a bit low, say .2v then you would have to have a cell that is .2v high, so you'd have 4.0 4.2 and 4.4, at that point your lipo would probably puff and be unusable. You can balance while you are charging, before you charge, after you charge, or just because you feel like it. I personally balance while I am charging. Balancers just plug into the balance tap, and no they don't go on the aircraft. It's more like a charger or something, ground support.

hopefully that answers your q