It seems you're asking about a Fallout 4 plugin called "FourPlay" (sometimes stylized as Four-Play) and its associated F4SE plugin.
Beyond the raw manipulation of skeletons and animations, the plugin serves as a critical dependency—a foundation upon which other mods are built. In the modding community, frameworks are the unsung heroes. The Fourplay plugin acts much like a driver for a piece of hardware; it handles the low-level communication with the game engine so that other mod authors do not have to reinvent the wheel. By exposing high-level scripting functions—such as starting a scene, positioning actors, or handling furniture—it lowers the barrier to entry for mod creators. A quest modder does not need to understand assembly code or memory addresses; they simply need to call the functions provided by the Fourplay plugin to trigger the events they desire in their story.
Advanced Animation Handling: It allows the game to recognize and play custom animations that aren't part of the base game's library.
Version Matching: Plugins are highly sensitive to the game's executable version. Always ensure you are building for the correct version (e.g., 1.10.163 for standard "Pre-Next Gen" or the latest 1.10.984+ for "Next Gen").