During checkout, the default configurations will let your customers checkout as guests. The customers will not be asked to login. If you wish to allow your customers to signup and save their entered information, you can turn off the option Allow guests only in the Store configurations > Checkout & cart, see the screenshot below:
When turned off, during the checkout process, your customers will be proposed 3 options before proceeding:
- Signup and create a new login
- Login and use their existing account
- Checkout as a guests
When customers create an account, their billing and shipping information will be saved and used during their next checkout. This will allow them to speed up the checkout process. On the administrative side, you can retrieve all the orders a customer made using the same credential on your website under Manage store > Customers. Click on a customer's email and you'll have access to the list of orders he made.