Whether it is marketplaces like eBay, Amazon, Rakuten and Lazada or ecommerce platforms like Shopify, Magento, WooCommerce and BigCommerce; all offer an API to integrate into their services.
But why are APIs so important?
An API is a way for two systems to communicate with each other to access each others services and data. A merchant using an inventory management system would typically connect that system to the webstore. Once connected, orders generated by customers purchasing a product, will immediately appear in the inventory system. The communication between these systems is done via an API.