On a regular WordPress site, when a new user logs in, he is created in the database. Then the email is sent to the new user with his credentials. Very simple. As it should be. The New User Approve plugin modifies the registration process. When a user registers on the site, he is created, and then an email is sent to the site administrator. The administrator is expected to approve or reject the registration request. An email is then sent to the user indicating whether they were approved or rejected. If the user has been approved, the email will contain login credentials. Until the user is approved, he will not be able to enter the site.
Only authorized users will be allowed to enter the site. Users who are pending approval, as well as rejected users, will not be able to access the site.
User status can be updated even after initial approval / rejection. Each user that existed before the activation of the new user will be considered an approved user.