Light energy can do one of three things when it encounters a substance. It can pass through without being diffused, it can pass through and be diffused, or it can not pass through.
A material that lets light pass through without diffusing, or scattering, the rays is said to be transparent. A very clean, colorless, clear glass window is a good example of a transparent material.
A material that will not let light pass through it at all is said to be opaque. A solid wall of bricks would be a good example of an opaque material.
A material that will allow light to pass through, but cause it to diffuse when it does--that is scatter the rays--is said to be translucent. Good examples of diffuse materials would be anything which you would use to pass light through, but not allow you to see what is on the other side:
A light bulb has a paint on the inside of the glass which diffuses the light which keeps us from seeing the very bright source of light inside.
A bathroom window may have a coating which diffuses the light passing through it so daylight can come in, but no one can see through the glass to what is inside.
In a light fixture there may be a plastic cover that diffuses the light so that it is spread out over a larger surface. This is why the lights in many classrooms have a plastic cover that "diffuses" the light to give an even coating of light on all of the desks in the room.
to put on windows e.g Net Curtains
lampshades are used to cover lamps
stained glass are used in churches to cover them