What is a VSIX file? Visual Studio Integration SDK
You use the VSIX format to package project templates, item templates, Visual Studio Integration Packages, Managed Extensibility Framework (MEF) components, Toolbox controls, assemblies, and custom types (this includes custom Start Pages). Then you can share your VSIX Package through the Visual Studio Gallery.
To use the VSIX format you will need to open Extension Manager, on the Tools menu, then click Extension Manager.
For example you could add the Visual Studio Power Tools, this free extension is a great way to add more to your Visual Studio .
To see more about the Products and Extensions for Visual Studio: