UVW map and Unwrap are tools for applying textures. UVW map when applied to a mesh will allow you to pick the method you want your textures to be mapped (planar, cylinder, sphere, ect) once you've done that you use a uvw unwrap to make final adjustments in the positioning of the parts (IE you can use this on a saucer so you only have to make one half of the saucer by selection half of it and flipping it over and repositioning it) it also allows you to select certain parts and remap them so that the texture better fits (primary hull, you can remap the deflector, move it to its own spot so that when you make the textures it better fits.) once that is done you can either take a picture of the UVW map or do what i do and use texporter to do the work for me.
Hope that helps
Robert