An API is an Application Programming Interface. It is a set of routines, protocols, and tools for building software and applications. A good API makes it easier to develop a program by providing all the building blocks, which are then put together by the programmer.
For each of the APIs links are provided to the associated syntax or Swagger documentation. Swagger is used to define a standard, language-agnostic interface to REST APIs which allows both humans and computers to discover and understand the capabilities of the service without access to source code, documentation, or through network traffic inspection. Other documentation and a client interface that demonstrates the associated API is also provided.