Neither \/ nor \? are control sequences in LaTeX*, causing the error. Instead, you're probably looking for:

\documentclass{article}
\begin{document}
\begin{description}
\item [\texttt{/} or \texttt{?}] - Search for a pattern of text, jump to it by hitting Enter
\end{description}
\end{document}
The above minimal example typesets / and ? in a monospaced Computer Modern (or typewriter-style) font, within the description environment's \item. Not sure what exactly your context is, but if you want to include the square brackets [...], use
\item [{[\texttt{/} or \texttt{?}]}] ...
instead. This puts the contents of the \item's optional argument in a group, rather than confusing TeX in using unmatched brackets and causing spacing problems:

* Well, \/ is a control sequence (using as an italic correction), but not the one you're after...