Microsoft Visual Studio Tools for Applications lets you add and run VSTA customizations in applications that are integrated with VSTA. VSTA has two primary modes of operation: with a supported version of Visual Studio installed and standalone. In standalone mode, VSTA provides the application with the means to load, compile, and run end-user customizations. With a supported version of Visual Studio installed on your machine, VSTA extends that functionality with the means to edit and debug those customizations.