"Normal" is a mathematics term. It means at right angles, perpendicular. It's much used in engineering and science calculations, since a lot of vector math and such is based on geometry. The line labeled n is the normal:

You can see from the illustration how this applies to 3d modelling. The normal shows which side of a polygon is the "right" side.

Weirdly, Poser doesn't actually use normals. It uses one-sided polygons or something like that. (I'm sure someone more knowledgeable will explain.) That's why the "reverse normals" function in some other apps (such as UV Mapper) doesn't work for Poser. The Poser "reverse normals" has the same effect that reversing normals in other apps...but it's not actually reversing the normals.

Okay, I probably just made it even more confusing...

I do like that outfit. I've been wanting a dress like that for Laura, actually. If it's dynamic, you should be able to use it with just about any character.