The term 'open API' in software development refers to an Application Programming Interface that is publicly available for use by developers. Open APIs facilitate the sharing of data and functionality across different applications and platforms, promoting interoperability and innovation. They allow third-party developers to create applications that integrate with a primary platform, enabling richer user experiences. Open APIs often come with detailed documentation to help developers understand how to use them effectively, thereby fostering a collaborative ecosystem that can benefit all involved parties through shared resources and tools.