A Program Member is any customer who has registered for an account with your store. (This means that they have signed up with an email and password.)
If you are using Shopify POS, customers can also become a Program Member via placing an order there.
Note: in order for a customers Online and POS points to be linked, a customer must be signed up online with an email and password.
Smile syncs data with Shopify, ShopifyPlus and BigCommerce.
This means that customers who create an account with your store will automatically be enrolled in your rewards program, and can begin earning points by creating a unique password for their account.
If the customer has not registered for a store account, they will be considered a Candidate and will not be able to interact with your rewards program until they create an account.