An organization (only parent org) can control who is allowed to create an account in your org using the generic signup link. This setting is located under the "Organization Configuration" tab in the ADMIN settings sidebar.
There are three different setting states:
If the slider next to "Enable Domain Signup Whitelist" is switched to off, this means that the whitelist restrictions are disabled. Someone can go to the signup link for that organization and create an account with any email.
If you are an ADMIN for an enterprise, this state doesn't really serve any purpose and is not recommended because anyone could sign up under your company account without being invited or even working there.
If you are a coach, we recommend sending invitations rather than a link, but this feature might be useful if you prefer sending a link rather than invitations.
2. Enabled without Added Domains
When a new org is created, this is the default setting. This setting means that no one can sign up and create an account using the URL. An invitation must be sent for someone to join.
3. Enabled with Domains Added
This setting state allows only people with emails under the saved domains to create an account using the generic signup link. Anyone outside that domain would need to be invited directly.
This added setting only controls the generic signup link for a parent organization, it does not restrict who is able to be a member of an org or who is able to be invited.