What's the difference between master and unique coupon types?

When creating a coupon on Attrac, you need to select the type: either a master coupon or a unique coupon.

A master coupon type generates a single coupon code that can be used by all customers. This type of coupon can be created on both Attrac and Shopify. On the other hand, a unique coupon type generates a distinct coupon code for each customer during signup campaigns. This feature is available in Attrac but not in Shopify.