Man pages and categories 1 & 8

[Julien ÉLIE]

Hi,

What is the difference between the categories 1 and 8 for man pages?
I see that we have references in our documentation for both rnews(1) and 
rnews(8), sm(1) and sm(8), innfeed(1) and innfeed(8), and so on.

What is the best practice to follow?

-- 
Julien ÉLIE

« Prouidentia, dum ortum ante obitum ponit, sapienter fecit, sin autem
   quid uitae sit notum ? » (Alphonse Allais)