Application Program Interface / Development Terms Application Program Interface An application program interface, or API, is a set of rules and protocols that allows one software application to communicate with another. APIs define how requests for information or functionality should be made, what data formats to use and how systems should respond. They act as intermediaries that allow different software components or platforms to work together without needing to understand each other’s internal code. APIs are widely used in web development, cloud services, mobile apps and software integrations. For example, when a weather app pulls real-time data from a government climate database, or when a payment gateway processes a donation on a nonprofit’s website, it is likely using an API to exchange information securely and efficiently. APIs can be public, private or partner-based. Public APIs are open for developers to use, private APIs are used internally within an organization and partner APIs are shared with selected third parties under specific agreements. REST and GraphQL are common frameworks for building APIs. APIs are essential for creating flexible, scalable digital ecosystems. They allow businesses to integrate tools, automate workflows and enhance user experiences without starting from scratch. For B2B SaaS companies, offering a well-documented API can attract developers and create new revenue streams. For mission-driven organizations, APIs enable integrations with donor management platforms, CRM systems and data analytics tools. A well-designed API is secure, stable and thoroughly documented, helping teams save time, reduce errors and deliver more powerful features to their users.