Create Concepts or Objects for Cars?

So, if I wanted to add car models to different racing games, do the cars get created as objects or concepts? I've seen some made as objects, so is that how they should be added? Sorry if this has already been asked; it didn't show up as a similar topic.

Object for specific cars and concept for their brand.

" Object for specific cars and concept for their brand. "

I was about to post about this, might add some wiki car pages.