typedef void __fastcall (*TModuleUnloadProcLW)(NativeUInt HInstance);
TModuleUnloadProcLW defines a procedure that can be called during package unload.
Before Delphi unloads a package that was used by your application, it can optionally call your TModuleUnloadProcLW routine. In essence, AddModuleUnloadProc adds your callback routine to the head of the list of internal routines that Delphi invokes to perform the unload.
Proc is the Handle to the DLL Package instance being unloaded.
The LW part of the name refers to the Long Word type of package handle. This is in line with Windows handles and the THandle type.