API stands for Application Programming Interface, and its primary function is to enable communication between different software systems. APIs specify the methods and data structures that programs can use to interact with one another, allowing apps to request and exchange information efficiently. This enables developers to integrate third-party services, access databases, or modify data seamlessly without needing to understand the internal workings of the systems involved. APIs are essential for modern software development as they facilitate interoperability and enable the creation of complex ecosystems, empowering developers to build innovative solutions that leverage existing functionalities.