}; used to delimit groups or arguments in (La)TeX code.
These are characters of categories 1 (left) and 2 (right). Conventionally, only
} have these respective category codes; occasionally, however, they are locally given to some other characters so that those characters may be used in some other capacity. See the index entries for "
}", and "braces" in The TeXbook.
"Implicit" braces are also possible; see implicit-braces, and the question When can one use implicit braces instead of explicit braces? in particular.
Also used to refer to mathematical symbols of vaguely similar shape to (but often much larger size than) the
} characters; see the TeXbook index entries for "
\}" and "
\brace", as well as the "in math formulas" and "horizontal" sub-entries under "braces".
Sometimes people use brackets instead of this tag, though that can also refer to the delimiter pairs
 (in the U.S.) and
() (in Britain), or even to any paired delimiters of this type. (We hopefully know better than to include
<> among their number in these parts; as such usage is generally a corruption of