Bender = special build of Slicer with additional modules for animation and physically realistic simulation of tissue deformations.
Bender includes readers for BVH motion capture files and armature files. The armature file format seems to be some VTK-based format, so it would need to be modified to be able to read some other format that Blender/3DSMax can export.
See a couple of videos about what it can do:
While you can do basic rigging and animation in Slicer (Bender), for more sophisticated animations it is probably better to work in Blender or other professional modeler software, export results to files, and import those into Slicer.