Script Hook V is a library required to run scripts created on ASI in GTA 5 on PC.
Installation: Copy ScriptHookV.dll to the root folder of the game (where GTA5.exe) To run ASI scripts, you need an ASI Loader, for this drop the file (dinput8.dll) into the root folder.
Grand Theft Auto 5 (GTA V): Script Hook V + Native Trainer v1.0.944.2 [1.0.335.2-1.0.944.2] {Alexander Blade} Free Download
There is also a sample ASI script in the archive – native trainer, to use it, just drop NativeTrainer.asi to the root folder (you can leave it if you have another in-game trainer).
In order to enter GTA Online, you must remove the ASI bootloader.
For patches: 1.0.335.2-1.0.944.2