Exploring Office development is like looking at a cross-section of an old tree; you'll find different layers from different eras, each carefully preserved for compatibility. Run the just-released Word 2016, enable the Developer ribbon, click VBA, and there is Visual Basic for Applications 7.1, using old-style VB as found in the long-deprecated VB 6.0 from 1998.
The venerable VBA lives on in Office 2016
VBA is well suited to automating Office, since it is built on COM (Microsoft’s object technology) and has fast access to the COM interfaces exposed by Office applications. There is also a great developer feature, which is the ability to record your actions as editable VBA macros. You can also write COM add-ins for Office applications in any language that supports COM, still fully supported in Office 2016.
Another approach is to develop Office extensions using .NET languages, via another technology called Visual Studio Tools for Office (VSTO). This one dates from 2003, and the last major version was 4.0 in 2010. VSTO projects also access the Office COM interfaces, but via interop which is slower. The languages and frameworks are more powerful than VBA but VSTO projects are applications which have to be installed, unlike VBA projects which are embedded in documents or templates. VSTO also still works fine in Office 2016.