• Straight Registration - Your clients go through the registration process to register a user into the software
• JIT Registration - Your clients start placing a classified and any "address fields" values inserted in the place a listing process auto populate the same of the user fields. The email value of the listing is used as the email of the user account. The client is asked to fill in a username and password fields in that same process. When the listing is placed the user is created.
• FaceBook Registration - This allows the client to use their facebook user to create an account in your classified or auction site. You would need to configure the social connect addon to make this feature available to your clients.
• Use no user accounts - You can turn on the use of the anonymous listing addon and your clients will not need to create an account to place a listing but lose all the extra features attached to a user.

• Can force admin to approve all registrations
• Can use the email verification system to verify the registrants email with or without the admin being notified of any registration attempts.
• Can send "registration complete" emails to the admin
• Can send "registration complete" emails to the new registrant

Most registration options are managed within the following admin tool:

REGISTRATION SETUP > GENERAL SETTINGS

Most pages in this subsection of the support wiki describe the features available within that admin tool page. There is additional registration setting here in the admin tool:

EMAIL SETUP > NOTIFICATION EMAIL SETTINGS > REGISTRATION VERIFICATION SYSTEM

That admin tool setting is explained further in this registration verification support wiki page.