A .vi is a single virtual instrument program. A .llb is a library of .vi's or controls with the .ctl extension. There are also a .vit and .ctt for VI templates and control templates. LabVIEW subroutines have a .lsb extension. All VIs are compiled. To create a LabVIEW exe or dll, you use the application builder. This comes with the Professional version of LabVIEW or you can purchase it separately.