\lmoustache \rmoustacheThe commands \lmoustache and \rmoustache are used to create left and right curly brace delimiters, respectively, that resemble moustaches. These are often used in mathematical expressions to group terms or to denote sets in a visually distinct way.
Grouping terms x and y with moustache delimiters
\lmoustache x + y \rmoustacheDenoting a set of elements a, b, and c with moustache delimiters
\lmoustache a, b, c \rmoustacheIndicating that the set of numbers 1, 2, 3 is a subset of natural numbers using moustache delimiters
\lmoustache 1, 2, 3 \rmoustache \subseteq \mathbb{N}