I'll try to explain this on the basis of the console command useradd; the manpage of useradd says:
useradd - Create a new user or update default new user information
now there are several options you can pass to this command. if you use graphical tool, then you must specify the options in the gui tool, so that it then creates the user on the base of those...anyway, I'll do this console-based. here's a cut from useradd's manpage:
"When invoked without the -D option, the useradd command creates a new user account using the values specified on the command line and the default values from the system. The new user account will be entered into the system files as needed, the home directory will be created, and initial files copied, depending on the command line options."
when you add a user, the shortest way is of course this:
useradd username
which whould create a user called username, and that's it. no home dir or anything _unless_ there are some default values set that tell useradd to do so...but basically you won't get a home directory, for example. if you want that, you would use the -d option:
useradd -d /home/homedir username
which would create a new user called username and set /home/homedir to his/her home directory...other options include -c (comment), -e (expire date), -g (initial group), -G (groups), -p (password), -s (shell), -u (uid) etc. etc. etc.
so the things you get when creating a user depend on what command line parameters you give to the useradd program. GUI tools work in the same way, but with the difference that you choose the options in the graphical window and then the GUI tool does these command line parameter thingies for you.
hopefully this explained a bit...you get what you ask, and if you don't ask for something (and nobody has set defaults for that action), you don't get that something
