A transparent substance allows almost all incident light that strikes it to travel through it. Most home windows are made of transparent glass. Cellophane is transparent. When looking at a transparent substance, you can clearly see what is on the other side of it.
A translucent substance allows only a small portion of incident light to pass through it. Many light fixtures use translucent materials to partially shade a light bulb, allowing a controlled amount of the light to pass through it. A small amount of water can be transparent, but waist-deep water is not as transparent; if you stand in waist-deep water and look down, you would not see your feet very clearly, because some light would not pass through water of that depth.
Light exhibits the property of reflecting from or bouncing off most surfaces. If incident light strikes a smooth reflective surface, such as a mirror, it bounces away from the surface in the opposing direction at the same angle. This property is analogous to a rubber ball striking a hard surface. Some glass-like materials are translucent; they reflect some incident light while allowing a portion to pass through the material.
An opaque substance allows no light to pass through it. A translucent substance can be thought of as the middle area of a scale that marks transparent and opaque at the extremes.