A repeat customer is a paying customer who has come back to your store to place additional orders after their first.
Getting one-time customers to come back is such a huge hurdle for ecommerce stores that it's important to track customers who have gotten past that.
Repeat customers are the same as returning customers in my opinion. Some people make a distinction between the two like returning customers have placed two to four orders and repeat customers have five or more orders. I feel like that distinction doesn't matter enough to give different labels to each.
Eric Davis
How do your products determine customer behavior
In Repeat Customer Insights the Customer First Product analysis will measure customer behavior based on the products each customer first ordered.