define-minor-mode: what's the purpose of the BODY argument?

[Raffaele Ricciardi]

Hello there,

the documentation of `define-minor-mode' begins with:

— Macro: define-minor-mode mode doc [init-value [lighter [keymap]]]
keyword-args... body...

Then it continues with documenting what the purpose of each argument is, 
but it
fails to do so for the BODY argument.  So, what's the purpose of that 
argument?
Is it code to be run every time the mode is activated or deactivated, 
and such
code can check `prefix-argument' to determine whether it should activate or
deactivate itself?

Thanks.