The htpasswd command is used to generate or modify a password file suitable for use with the htaccess access control mechanism.
The htpasswd usage is as follows:
htpasswd [-c] passwordfile username [password]
Where, -c creates a new passwordfile(overwriting an old one if it exists). Without -c, the command will modify the existing file by either updating the user's password (if user already exists) or adding a new user with the given name. If the optional password argument is not given, it will prompt interactively for the password to assign.
htaccess is not the preferred access control mechanism in Web Server. Wherever possible, use ACLs instead.