You gave the option to either manually or auto approve new customers that sign up to your website.

Auto approval.

This.This lets anyone register on your site.
If you sell goods to all countries this also lets them purchase from the store.

You can turn this on / off via the ‘Customer Group’s area. Further details about Customer Groups can be seen at:

Admin > Sales > Customer Groups (click ‘edit’ beside the default group)

Under the Approve New Customers:
Customers must be approved by and administrator before they can login.
select Yes or No.

You can view more details about Customer Groups at:

http://sellerbot.com/support/knowledge-base/customer-groups/

Manual approval.

This means a person is unable to purchase anything from the store until you manually approve their account. 

The best use of this is for high value items as it adds another fraud detection step to the order process.

However it may turn some customers off as they are unable to purchase until their account has been approved by the store admin.

To manually approve a customer you need to go to:

Admin > Sales > Customers

1. Tick the check-box beside the customer you would like to approve
2. Click the ‘Approve’ button

You can view more details about editing customers at:

http://sellerbot.com/support/knowledge-base/customers/