Language Semantics: @ symbol??

[Enigma Curry]

Sorry, for the noob question, but I haven't been able to find
documentation on this matter.

I've been looking for documentation that describes what the @function()
syntax is all about.

I've seen this on a few pages, for instance:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/307871

and also in TurboGears:

http://www.turbogears.com/docs/wiki20/page5.html

The general format appears to be:

@somefunction()
def a_newfunction():
    ....

What does it mean and what does it do?

Thanks!