Why are *nix commands referred to as Man(1), Diff(1), Cat(1), etc

Question

Possible Duplicate:
Why do programs in Unix-like environments have numbers after their name?

What does the (1) mean?

Answer 1

It's the manual section its man page lives in. From man man:

   The table below shows the section numbers of the manual followed by the types of pages they contain.

   1   Executable programs or shell commands
   2   System calls (functions provided by the kernel)
   3   Library calls (functions within program libraries)
   4   Special files (usually found in /dev)
   5   File formats and conventions eg /etc/passwd
   6   Games
   7   Miscellaneous  (including  macro  packages and conven-
       tions), e.g. man(7), groff(7)
   8   System administration commands (usually only for root)
   9   Kernel routines [Non standard]