Most FiveM servers use Lua , a lightweight scripting language, to create everything from custom car handling and player menus to complex economy systems.
FiveM uses a modified version of Lua 5.4, often referred to as CfxLua , which includes performance patches and extensions specifically for the game engine.
Understanding fivemlua.exe: The Engine Behind Custom GTA V Experiences
At its core, fivemlua.exe is the for the FiveM platform .