32bit and 64bit

Autodesk Revit software is specifically built for Building
Information Modeling (BIM), helping building professionals design,
build, and maintain higher-quality, more energy-efficient buildings.
Autodesk Revit is now available as an application that combines
the capabilities of Autodesk Revit Architecture, Autodesk Revit MEP,
and Autodesk Revit Structure software

http://www.autodesk.com