The Customers screen is how you create and manage accounts for customers of your online store. Customers may also create their own accounts while visiting your online store. The Customers screen is also where you manage Business Accounts and Availability Groups.
Customer Accounts are how you track a customer's order history, saved credit cards, customer credit, mutliple addresses and subscriptions for an individual customer. While it is not required that a customer has an account with your store to place an order, it makes it easier for repeat customers because all of their data is saved and can be re-used on their next order.
To reach the Customers screen, click the Customers header on the left side of the page.