It Loads the specified DLL(Dynamic Link Library) into WinRunner. In order to use the dll, we will write all the functions in dlls in C or C++. Once we create the dll we need to load the dll to access all the functions written in that dll. WinRunner provides the functions in the same way. They(MI) write all the functions in DLLs and once Winrunner starts, it loads all these dlls.