# useradd richard
is the simplest syntax. It will create a new user "richard" with a unique
UID, and new group "richard" with a unique GID. It creates a new directory
/home/richard owned by "richard" and stuff it with files found in /etc/skel,
etc., etc.
Then, richard needs a password:
# passwd richard
New UNIX password: <type new password
here>
Retype new UNIX password: <type it again,
since it's not echoed>
passwd: all authentication tokens updated
successfully