The scale indicates the size of the diecast car. So when talking about the 1/18 scale, it means that one centimeter on the diecast Paragon is 18 centimeters in reality. To give you an idea Paragon diecast 1/18 scale measuring between 25 and 30 centimeters depending on the model and Paragon diecast 1/43 scale measuring about 10 centimeters. More scale is the higher more the car will be small. The links below allow you to filter your search by Paragon diecast scale.
1/18     
1/43