You often want to out-comment some stuff while writing a LaTeX document very quickly, and LaTeX does only offer single-line comments out of the box:

% This is a comment
% This is the next line

Of course this can get a lot of work if you do this manually for a lot of lines. There might be editors that ease this, but I just found a very easy way to achieve multiline-comments using the verbatim package:

\usepackage{verbatim}

You can now just have multiline comments like this:

\begin{comment}
This is a comment
This is the next line
\end{comment}

Very easy. I knew there had to be a package for that. I was just too lazy to search for it up to now.