Auto Generate Password
This will remove the password field from registration forms and WordPress will automatically generate and send a random password to the user after successful submission of the form.
WP Registration Auto Approval
Turning this toggle button off will disable automatic activation of WP user accounts. Admin will have to manually activate each account by browsing through the submissions. Comes handy, if you want to manually approve each submission for registration.
Send Username and Password to User Through Email
If site admin wants to send username and password information to the user after registration as plain text, then this setting should be turned on. Many people avoid sending username and password as plain text because of security reasons. This email is separate from auto-responder email sent to the user which admin can configure.