I don't have a problem with my system, I'm just wondering. For example, here is my passwd file

root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
sys:x:3:3:sys:/dev:/bin/sh
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/bin/sh
man:x:6:12:man:/var/cache/man:/bin/sh
lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh
news:x:9:9:news:/var/spool/news:/bin/sh
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
proxy:x:13:13roxy:/bin:/bin/sh
www-data:x:33:33:www-data:/var/www:/bin/sh
backup:x:34:34:backup:/var/backups:/bin/sh
list:x:38:38:Mailing List Manager:/var/list:/bin/sh
irc:x:39:39:ircd:/var/run/ircd:/bin/sh
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh
nobody:x:65534:65534:nobody:/nonexistent:/bin/sh
james:x:1000:1000:James,,,:/home/james:/bin/bash

Where are there all these users? That drives me crazy. I would ideally like my passwd file to have USERS in it, not all these random things.

Can someone explain the theory behind this?

Thanks

In most cases the theory is to have user accounts that are set up for specific purposes. The most important ones for a desktop are the root, man, and nobody accounts. Some of the other accounts can be removed but don't experiment until you do some research on each account. For example believe it or not the man utility requires the man user account in order to work as it is originally installed. I found that out when I changed the permissions on the /usr directory and found that the man utility didn't have permission to read the man files! The nobody account is good because it is the least privileged account. It is useful for running the updatedb utility. You can prevent the updatedb utility from reading the files in the /home directory if you change the owner of the /home directory to root:users and change the permissions on that directory to 770. The nobody account does not have any privileges so it can only access files that have at least read permission for "others".