It doesn't modify the original game files. It simply "hooks" into the process while the game is running.
It provides access to "natives"—the built-in functions Rockstar uses for game logic—enabling mods to manipulate everything from weather to player physics. script hook v 101180
Script Hook V is the foundational library that allows custom .asi plugins to run natively within Grand Theft Auto V. Version corresponds specifically to the "Legacy" (Pre-Enhanced) build of GTA V (game version 1.0.1180.2). It doesn't modify the original game files