Hello Colin
The "normal" devices are delivered in their original packaging and are not shrink-wrapped and touched by anyone in this country - in other words: brand new.
A showroom device has been unpacked by someone and installed in the showroom at Digitec and, depending on this, more or less people have had it in their fingers - the devices are certainly cleaned or cleaned on the outside and then repacked (probably not welded!) - but they are not completely "pristine".
There may be differences in the battery (you would have to ask Dicitec) in terms of "showroom: was operated on electricity and charged several times"... and of course the price (showroom a little cheaper).
Hope that helps and LG