An Offer is the template of a Subscription.
When a Customer subscribes to an Offer, it makes a Subscription.
The Subscription is related to a Customer and an Offer.
You can modify the Offer, it will not modify the Subscription of your Customer.
You can modify the Subscription of a Customer, it will not affect the Offer related to this Subscription.
The Subscription is a copy of the Offer made when the Customer subscribed.
See ‘ProAbono – Core Concepts’.