netbeans.exe is the Windows launcher for NetBeans. Basically it assembles the class path string for starting up NetBeans, passes the command line arguments, etc., and launches Java with those arguments.
The main reasons for the exe are:
- Start NetBeans without a console window opening as well as the main window
- Windows shell quoting is inconsistent across versions of Windows
- On some versions of Windows, command line length is limited to a shorter length than is sometimes needed for all the command-line arguments that should be passed to java
- Provide a thing you can double click that has the correct icon
It's nothing terribly exciting, it's just a small C++ app; the sources are in core/launcher.
There are actually two executables - nb.exe and netbeans.exe. netbeans.exe will suppress the console window (so you won't see any logging on the command line); nb.exe will show the command line. Under the hood, netbeans.exe invokes nb.exe (so don't rename it).
Source: NetBeans FAQ