It sounds intimidating at first because other OO languages like C++ or Java doesn't have such concept or construct built in. So what's about it?
def dec_func():
...
@dec_func
def func():
...
function 'func' is being decorated by function 'dec_func'; it is equivalent to "func = decf_func(func)".
The key concept is this:
@ is just a little syntax sugar meaning "pass a function object through another function and assign the result to the original function."
It brings the idea of "applying code to other code" (i.e.: like C macros) into mainstream thinking by formalizing it as a language construct. See the link
