Rum: Backset, Dunder And Lees

[mikeac]

So I've been trying to come up with a better rum process, My first rum was damn good, but looking to improve to well...DAMN good. But I'm a little confused by these three terms and people seem to use a lot of them interchangeably so I'm looking to clarify:

Lees: Crap on the bottom of my primary fermenter I leave behind when i
siphon into a carboy to let it clear a little? ( I thought it was all dead
yeast, apparently a lot of it is still alive?)

Backset: (noun) Crap left in my bioler after I'm done a run.
(verb) adding the (noun) back into a wash as liquid in a new.
ferment

Dunder: now this is where the confusion comes in...I've heard people refer to both lees and backset (assuming I have them right) as dunder. So all I really know is that dunder is something rum specific added to the ferment recycled from the previous run/ferment.

It seems people seem to use either/or as dunder and claims it makes the rum much better. I'm not sure which is actually dunder, and which to add back to my rum...Both?