The rundown...

[Diva_Admin]

In Poser there are a variety of different items you may have in your runtime.

Most often you will have "base" characters. (Victoria 4, Micheal 4, etc.)

Then you can add onto these base characters with things like; character morphs, clothing, hair, poses, etc. And more often than not these things have add-ons as well, like different hair colors for hair, and textures for clothing.

Most clothing items are character specific. Meaning, and outfit that works for Aiko 3, will more than likely not fit Victoria 4. There are programs out there that can convert clothing to fit other characters; like:

http://www.philc.net/WardrobeWizard.htm

http://www.evilinnocence.com/xd/