What does the @ symbol mean in LaTeX? I'm looking at the source of apa.cls, and there's a declaration:

\newsavebox\gr@box

and later on

\sbox\gr@box{\includegraphics[width=\linewidth]{#2}}.

It seems like @ isn't acting as a normal character, but I can't figure out exactly what it's doing, and couldn't find anything after bit of googling (how I would love a Google regex feature!) Thanks.

EDIT: Thanks for the help; of the links I looked through I found http://www.tug.org/pipermail/tugindia/2002-January/000178.html to be very helpful and concise. To summarize, the @ character is not normally allowed in the names of macros, so as a hack for scoping, LaTeX packages declare it internally to be a valid name character and use it for their macros. You can use \makeatletter in a document to access these macros, but you obviously must be very careful since you have can now overwrite essential LaTeX kernel macros; use \makeatother to revert.