Royalty Free Licence

Hi everyone, I started on Blender recently and enjoyed creating things. I think that the cgtrader community is great. I wanted to sell my own design of a low-poly car. It is not based on any real-life models. Completely my own design. I was almost about to post it, but then I came to the license part. I am very confused about what a royalty-free licence is. Do I have to pay to get this licence? If it's my own design do I need to buy a licence? My car is meant to be put in games and stuff, and I wanted to sell for a low price because it wasn't an actual model of a real-life car. I really need help. I don't want to be in trouble for claiming to have a licence but don't. And if I don't need a licence what should I put for the licence part. And if I do need a licence, where can I get one.

Thanks!