The \item command starts a new item in a List Environment. The optional argument label generates the item label; if not given a default label is used.
A blank line preceding an \item command has no effect.
In order to use brackets as part of the label (for example, in the Description Environment) they must be enclosed in braces:
\item[{[}item 1{]}] This is the first item
The \item command is fragile.