What is API? Leave a Comment / IoT / By Franchezka Revereza Application Programming Interface is a set of functions that allows applications to access data and interact with external software components, operating systems, or microservices. To simplify an API delivers a user response to a system and sends the system’s response back to a user, You click “add to cart” an API tells the site you added a product to your cart, the website puts the product in your cart, and your cart is updated. (online pharmacy australia free delivery)