What is the direference between 2D skins and 3D models and yes a did read the carpark faq but still i dont understand it
It's simple really :
A 3 dimensional model of a vehicle is this:
It's the 3D (width, length, and height) shape of the car, but no colour.
And here comes a 2 dimensional skin:
It's a flat 2D image (length and height) with all the colour, but no shape at all.
Put the 2D skin over that 3D shape and you get...taddaaaaaa:
...a vehicle with a 3D shape, and a 2D colour.
Think of your own body. The skin is the flat suit of outer flesh that gives you colour, and somewhere for your hair to grow. It has colour, but it's just a living suit for your body. However, it's the 3D vehicle of the skeleton, and muscles under the skin that gives you the shape that you are.
...and you need both.
What is best to use in TMU for a custom car, 2D skins or 3D models ?
...and you need both. If you just wish to paint cars, you use any graphics app to apply colours and images to the car skin (think of it as a tattoo on your body). Just flat images painted onto a surface, that's all a skin is, although those who don't understand the difference between the two have done their absolute best to confuse everyone else by mixing them up.
In TM the skin is the diffuse.dds inside the car zip.
The really difficult part is creating the 3D shape of the vehicle. In TM the 3D shapes are the the two Gbx files inside the car zip (high and low quality so two 3D models are required). You need a 3D vehicle, then you have to paint it. Both. Not one, or the other, and no confusing the two.