Regarding your question, materials come in three types. Transparent, translucent, and opaque.
Transparent materials are materials that allow light to pass through easily. Window glass is a good example of a transparent material.
Opaque materials do not transmit light easily or not at all. Most materials that you interact with on a daily basis are opaque. Wood and drywall are opaque materials. That's good, because otherwise houses would be see through.
Translucent is a sort of middle ground between the above two material types. Some light can pass through the material, but some of the light is scattered and/or absorbed. That's why translucent materials are sort of see through. Wax paper is a good example. Frosted glass is a another example that works. Plastic bags that you are given by the grocery store work too. Chances are the lamp shades that you have in your house are translucent too. They allow some light through, but not the full force of the bulb.
We can classify butterpaper, plastic bags as translucent materials.
Explanation: Materials are of three types.
Opaque: These are materials through which no light can pass through. For example, if we keep a wooden block in front of a ray of light, the wooden block will block the passage of light.
Translucent: These materials allow some light to pass through them. If we hold a plastic bag in front of a ray of light, only some light can pass through it.
Transparent: These materials allow light to pass completely. If we hold a clean glass piece in front of the ray of light, we can see that it allows light to pass through it completely.