What does 's' stand for in auto-complete tips?

When I use auto-complete in Emacs, there come out "s" "v" "f" as description? If you have ac, type some lisp function in *scratch* and ac show you the tips, there is a "s" there, t开发者_如何学JAVAype add for example, and ac helps to come out "add-hook" and so on...

f means function, interactive ones?

v means variable.

what about s, functions without interactive?

And... how to get the document of a "s" function, like "cc-mode"? C-h f failed.

There is a chart in section 9.8.7 (near the bottom of the document) here: http://cx4a.org/software/auto-complete/manual.html that says that s means symbol.