What is customer login?
By default, all your customers get a login to your online shop when they place an order.
With that login, they can log in if you link to your "Customer login" page.
Once logged in, they can see previous orders and their status. They will also be able to view and cancel any subscriptions if you sell those in your shop.
The customer will also automatically fill in their basket information when they place new orders.
It is optional if you want to display a link to your customer login page in your online shop.
You can also disable the entire account creation function in your online shop so that new customers do NOT get a login when they buy something. This is done under "Settings > Shop".