Libretro is an open-source software framework that allows developers to create and run video game emulators and game engines. It provides a unified API, making it easier to develop cross-platform applications that can run on various devices, including PCs, consoles, and mobile devices. The core of Libretro is the RetroArch application, which serves as a front-end for accessing different emulators, known as "cores." Users can download these cores to play games from various systems, such as NES, SNES, and PlayStation, all within a single interface, enhancing the gaming experience.