Think of it like this, The obj is the model, The cr2 is What changes the model useing the diles in poser and morph targets, When poser loads a morph target it is saved to the cr2 file, When you load the cr2 file you are telling poser that this is the configuration I want the obj file to have. So in order to add a morph target to a figure in poser the obj file is changed useing the cr2, the model that loads into poser is a changed version of the original obj file. Pz3 file is a scene file, It saves everything in the whole scene including the lights,cameras,props,textures,models ect.