It stands for low-level dueling. There are lots of people who rather than duel at high levels, they duel in much lower levels. IIRC, VLLD stands for very low level dueling (lvl 9) and then there are a few other variations such as lvl 18 duelers, lvl 30 etc, I can't quite remember each one.
in LoD, since itemlevels cover much more of the spectrum(1-99) and more people achieve 90+ levels then in classic, LLD is much broader. I think some even include up to level 50 or something into the LLD range.
in classic, the unique itemlevels range from level 1-30, so LLD is generally considered much lower.
Personally I define a LLD as a char which has access to half of or less then half the itembase and half of or less then half the skills. So 9-17 is lld imho, 18-29 mid and 30 and over just dueling/duelers.
The chalenge is to make the best dueler possible with this limited itembase.
There is a lot of intepretation of what constitutes LLD, and generally in dueling LLD you duel within level bands.
These bands usually correlerate with the levels at which you get skills.
You get normally LLD chars at levels 9, 12, 15, 18, 21, 24, 29 (Just before final skills) and 30 (depends on realm as to wether this is LLD).
LLD opens up several character types that cannot compete in higher levels duels, and also presents a challenge of getting obscene damage out of a level 9/18 character.
With the exception of Level 29 LLD is mostly dominated by melee characters as skills are thin on the ground and spells do very little damage. At level 29 a number of gear choices open up the possibility of making high damage caster characters - SOJ for example.
PFS > Yeeeee know tuuu much fer somebody that doesn't play anymore.
Indeed, what you describe is the absolute and (politically) correct version of what LLD is.
I would like to add that on non-ladder classic, there are old uniques(they do not drop anymore) which do not have a level requirement and can give a low level char a big advantage over other players. (I'm considering no level requirement SoJs, Etliches, nightsmoke, steel, snap, twitch and maybe shard[only 20fcr on the old ones though]).