You may also want to download the manual for Poser5. It's got a very good intro on what 3D on puters means. Poser is mainly used for organic forms, mostly human. You can use morphs to change the body appearance, you can give it a pose, you can texturize it, create a light setup you prefer etc etc. It ranges from as good as photorealistic over cartoon to sci-fi and fantasy. Probablt the best known character in the Poserworld is "Vicky", a mesh created by Daz3D. But Poser itself already comes with many characters, most of which are more cartoonish than realistic, except for Poser5. But Poser5 offers more options and you definately need a fast puter with lots of ram to use it comfortably.

I have tried prudent planning long enough. From now I'll be mad. (Rumi)