Win32 is a programming interface and application programming interface (API) for developing 32-bit applications on the Windows operating system. It provides developers with the tools to create software that can interact with the system's hardware and manage resources like memory and files. Introduced with Windows 95, Win32 allows applications to run in a multitasking environment, enabling users to run multiple programs simultaneously. It supports various programming languages, including C and C++, making it a versatile choice for software development on Windows platforms.