A DotNetNuke portal / website offers multiple "modes" for supporting User Registrations.

You can offer to visitors of your website to sign up for a website user account.  You can use these user accounts in many ways:

User accounts can be used as an email list for email messages.
You can create "members only" areas of you site that contains content hidden to non-members.
You could grant editing priviledges to selected areas of the site and share the ability/responsibility to edit and keep the site up to date.

There is often a concern that if Users can create their own accounts, that it will get out of control and numerous people you don't know will sign up or other possibly undesirable things. The DotNetNuke software gives you several ways to control or avoid these situations.

There are four (4) modes of User Registration.  These are set in the Admin menu > Site Settings > Advanced section.

Security Settings > User Registration

The four modes are:

1. None:
There is no way for a site visitor to register as a user. The "Register" button does not appear. All users must be created manually by a member of the site "Administrators" security role.

2. Private:
A site visitor may create their own user account. However, user cannot log in until a site Administrators reviews and approves the new user account.

During Registration the following message appears.

Membership to this portal is Private. Once your account information has been submitted, the portal Administrator will be notified and your application will be subjected to a screening procedure. If your application is authorized, you will receive notification of your access to the portal environment.

3. Public:
A site visitor may create their own user account. Access to the site is granted instantly and without limits.  There is no control on user account creation.

During Registration the following message appears.
Membership to this portal is Public. Once your account information has been submitted, you will be immediately granted access to the portal environment.

4: Verified:
A site visitor may create their own user account. An email with a unique access code is generated and emailed to the user.  The first time the user logs in, they must supply the verification code.  This process ensures that users creating an account are suppling a valid email address and they are the person with access to that email account.

During Registration the following message appears.

Membership to this portal is Verified. Once your account information has been submitted, you will receive an email containing your unique Verification Code. The Verification Code will be required the first time you attempt to sign in to the portal environment.

Site Administrators may delete user accounts that are not "authorized".  That is, the account was created but the user never logged in and entered the verification code.