The VTS subdirectory within the VTS installation directory (i.e. "C:\VTS\VTS") is known as the VTS layer directory. The VTS layer directory contains all of the common generic code for standard VTS applications, and is actually an application layer upon which all standard applications are based. Information on the VTS layer directory can be found in VTS Layer Directory.
Note: As indicated above, within the VTS installation directory resides a second directory named "VTS". It is important that the distinction is made between the VTS installation directory (which may be titled VTS or VTS 6 or another name that you specified during the installation), and the VTS layer directory that resides within the installation directory. The VTS layer directory is the main VTS application layer upon which all standard applications are built. It enables each application access to the standard services and features of the VTS software (such as security, the configuration toolbox and tools, and the Display Manager). Detailed information on the VTS layer directory can be found in VTS Layer Directory.