Line-oriented.

\fbox{
Just
a
test
}

\fbox{
Just
a
test

\linebreak
another parargraph
}

The "another parargraph" will still follows the "Just a test", forming a single line box

Whereas the \framebox, \makebox and savebox commands process their text arguments in LR mode, the minipage environment and the \parbox command process their text arguments in paragraph mode.

To place a box around the following use \fbox + \minipage

\bi
\item Instances map to points in $\Re^n$
\item Less than 20 attributes per instance
\ei

\begin{center}
\fbox{\begin{minipage}{5in}
[...]
\end{minipage}}
\end{center}