Traditional Unix systems typically store their user and group information in the
/etc/group files—and if you go looking, you can find these files on your Mac. However, after Mac OS X boots, it does not use these files. Instead, it uses Open Directory (discussed in Chapter 7) to store its user and group information. This allows the system to work equally well in home setups where there is only one machine and in enterprise environments where there might be hundreds of machines that use a central server for authentication.
While there are many ways to manage users on Mac OS X, the simplest and most direct by far is to use the Accounts preference panel.