What is an Application Programming Interface (API)?

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Application Programming Interface Definition

An application programming interface (API) is a set of defined rules that enable software programs or systems to talk to each other. An API serves as an intermediary layer between two systems, enabling companies to share their application’s data and functionality with third-party developers and business partners securely. APIs simplify integrations between enterprise systems by providing the architecture or protocol for how applications should share information. The most widely used API architecture is referred to as REST.

The four different types of APIs used in web services are:

• Public APIs – Open and available for use by any outside developer or business
• Partner APIs – Only available to selected and authorized outside developers or API consumers; partners have clear rights and licenses to access these APIs
• Internal APIs – Intended only for use within the enterprise to connect data internally
• Composite APIs – Combine two or more APIs to develop a sequence of operations