Glossary > 

A translucent material transmits light, but unlike a transparent material, it also scatters the light so those objects behind the material cannot be seen clearly.

Glass on the right has a light green translucency.

Raytrace materials can simulate translucency. A Raytrace material's Translucency color component ignores surface normal directions, giving the effect of light scattering.

You can also obtain translucency effects using the Standard material's Translucent shader.