You can specify a user group or groups that will be automatically assigned to a newly registered customer. User groups set access to certain categories, products, quantity discounts, blog posts, shipping methods, etc. Thus, you can restrict access to the store for new customers or, on the contrary, make some entities available only to them.
For example, you would like to encourage new customers to register in your store and are ready to give a 5% discount. You need to create the "Beginners" user group and a special promotion for this group. After that enable "Beginners" for the Default user group add-on setting. If a customer registers, the "Beginners" user group is automatically assigned and the order total is reduced by 5% at the checkout.