Just as humans have always preferred co-existing and communicating ideas, looking for and providing pieces of advice from and to their fellow humans, applications nowadays find themselves in the same situation, where they need to exchange data in order to collaborate and fulfill their purposes.

At a very high level, applications’ interactions are carried out either conversationally (the case of REST APIs), where the information is exchanged synchronously by asking and responding, or asynchronously via notifications (the case of event-driven APIs), where data is sent by producers and picked up by consumers as it becomes available and they are ready.