how this apple script work . what is the use of it
MacBook Air 13″, macOS 14.3
It is not an AppleScript, it is C++ code and Apple's Script Editor is only used for real AppleScript, AppleScript/Objective-C, and JavaScript for Automation source code.
That C++ code when compiled with an Apple clang++ compiler simply outputs "Hello World" to the Terminal from where it was compiled and run.
You will need a proper text editor (e.g. free BBEdit) and Apple's command line developer tools in order to edit and compile this C++ source code.