Fields Login and Password are required to post messages. If you only want to read public messages you can leave all fields blanc.
If you publish ICQ, Real Name E-mail and URL this information will be available for all users.
You can use address amd private messages. To address message to another user you should specify his Login (sic). To make this message visible only to this user you should set "Private" flag.
Reply field is used to build threads.