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
See how the month a customer orders will change their behavior
Repeat Customer Insights will automatically group your customers into cohorts based on when they first purchased. This will let you see how the date customers bought would impact their behavior.