text: An open API (often referred to as a public API) is a publicly available application programming interface that provides developers with programmatic access to a (possibly proprietary) software application or web service. Open APIs are APIs that are published on the internet and are free to access by consumers.
  Alternative Definitions
  There is no universally accepted definition of the term "Open API" and it may be used to mean a variety of things in different contexts, including:
  An API for use by developers and other users with relatively few restrictions. It may require registration or enforce quotas and rate-limits, but registration is free and open to all; or
  An API backed by open data. Open data is freely available for everyone to use and republish as they wish, without restrictions from copyright, patents or other mechanisms of control; or
  An API based on an open standard, which specifies the mechanism by which a consumer queries the API and interprets its responses.
  Open API versus private API