Commerce is a flexible and extensible platform, and just like Craft we have provided hooks and events to enable developers to add features to the system.
Events Reference — Listen for Craft Commerce events and run PHP code.
Hooks Reference — Modify Craft Commerce behavior.
Purchasables — Add an element to the system that is sellable.
Adjusters — Make any price adjustment to an order.
Shipping Methods — Add 3rd Party shipping methods and return shipping prices.