A transparent physical material shows objects behind it as unobscured and doesn't reflect light off its surface.
Clear glass is a nearly transparent material.
Although glass allows most light to pass through unobscured, in reality it also reflects some light. A perfectly transparent material is completely invisible. A translucent physical material shows objects behind it, but those objects are obscured by the translucent material. In addition, a translucent material reflects some of the light that hits it, making the material visible. Physical examples of translucent materials include sheer cloth, thin plastic, and smoked glass.