Translucency is a form of diffuse transmission where light passes through a thin object. This effect is often used to simulate things like leaves, paper, and thin plastics.
This parameter is the resulting color of the surface. You can choose a color or connect a texture or some other procedural pattern.
When light passes through a thin object, you may see shadows or silhouettes from the other side.
Roughness can make the light from the other side appear to scatter more or be blurrier.
Roughness examples : 0.0 / 0.2 / 0.8 / 0.6 / 0.8 / 1.0
Here is where you supply a signal, either a texture or procedural pattern, to create a bump to the surface to "fake" surface details like small bumps or scratches. This means an artist doesn't have to model these tedious and often repetitious parts of a model.