Software licenses are the most common type of products sold on subscription. Typically a customer will purchase a software license that renews annually, or is automatically renewed each month until cancelled. Physical products, such as nutritional supplements, can also be sold as subscriptions.
Any product having a Payment Plan is a subscription-based product. Once the product is purchased, a subscription record is created in order to keep track of each recurring billing transaction, and the state of the subscription.
You have the flexibility to offer your customers more than one subscription model for the same product. Suppose you are selling a one-year subscription to an educational course on "Techniques for Increasing Sales Lead Conversions", and you want to allow your customers to either pay for the one-year access up front, to pay for it once a quarter, or once a month. You wouldn't necessary create three different products for each payment option because it's still the same course regardless of how your customers pay for it. Therefore, you will create three different payment plans and offer your customers the choice of all three at checkout. Maropost for Commerce will automatically keep track of which payment plan each customer selected and then do the recurring billing at the appropriate time.