A customer is a person or organization that has purchased from your store.
It is important to separate them from people who have not purchased yet. While you might treat them the same, they are merely prospective customers and cannot be measured as customers yet.
The vast majority of ecommerce customers are one-time customers who have only one order, while the rest are returning customers or repeat customers.
Eric Davis
Market to your customer's timing
Figure out how long customers wait in-between purchases and you have a key component for your marketing timing. This is the basis of the Average Latency metric and Order Sequence Report in Repeat Customer Insights.