On the registration page, what does Profile Visibility mean?

If you make your Profile visible, other members will be able to find you in the Member Directory. They will also see a link to your Profile next to any resources, conversations, news items, or events that you post. If you select No when asked whether you would like your Profile to be visible, other members will not be able to see your Profile or contact you.

You may log in with either your assigned username or your e-mail address.
The password field is case sensitive.