When talking about API management, the first thing that comes to mind is a public API, one that is open for anybody to consume, provided a certain level of registration. Obviously, the most famous APIs are the public ones, potentially known to anybody. However, such APIs only represent a small subset of all APIs that need to be managed. Many APIs that we encounter in the field are setup in such a way that their consumption is restricted to a specific group of developers. This happens for various reasons. Some talk of public and private APIs, others use the terms open and closed to represent the same distinction.