Subdivide All

Subdivides the entire object regardless of current sub-object mode.  See the image below for a simple example.  Typically you will do this to add additional detail to your model.

Subdivide Selected

Subdivides only the selected faces.  See the example below where we have subdivided a single face.  You may or may not want to fix resulting 5 sided polygons.

Created with the Personal Edition of HelpNDoc: Create iPhone web-based documentation