Low Level Dueling
From Diablo Wiki
Low Level Dueling, or LLD, is the practice of dueling characters at a pre-set maximum level to limit their equipment choices and skill options. Common levels are 9, 18, and 30. See also vLLD, MLD and Twink.
Such duels are highly item-dependent, and expert LLD players will have completely optimized their charms, socketed items, and more, turning their low level characters into damage-dealing monsters who are far more powerful than any normal character of their level could ever hope to be.
Advanced LLD players will have rushed their low level characters through hell difficult to gain the benefits of the +skill, +attribute, and +resistance quests on all three difficulty levels.