VSTA is the acronym for Visual Studio Tools for Applications and is the replacement technology from Microsoft for VBA (Visual Basic for Applications).
http://greenrevit.blogspot.com/2008/02/revit-2009-new-feature-vsta.html
Typical uses for the SDK kits can be anything from custom families to a custom interface.
Do you have programming experience?
What are you trying to do?
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(defun botsbuildbots() (botsbuildbots))