There are different types of APIs, but what do they really mean? Free API Services are one type of API. But, what does that actually entail? To understand, let’s first take a look at the different types of APIs: public, private, partner, and composite. Public APIs are open for anyone to use and don’t require authentication. Private APIs are used internally by organizations and generally require some form of authentication such as an OAuth token. Partner APIs are an evolution of Private APIs, but are made available to a third party for use. Composite APIs encompass all of these types of APIs and even more. They’re a combination of existing APIs to create a new one. They can be public, private, partner, or composite in nature. For example, you could build a composite API with your private data, public data, and partner data. This would make it a public composite API that is powered by your data.