The Guest Checkout functionality allows a user to place orders without having to create a user account . This means they don't have to login to place an order.

You can enable / disable Guest Checkout in Settings: 

There are additional settings to dictate whether Guest Users' email addresses are saved in Customers > Customer Management against their guest account.

These are only accessible by the Infigo Support Team. If you would like us to update these settings then please submit a ticket with the subject: "ordersettings.anonymouscheckoutallowed"