Transparent materials are those that let light through with very little or no diffusing or scatterng of the light. This means that you can see clearly through a transparent material.
Translucent materials are those that let light through but in the process it is diffused or scattered. This means that you are unable to clearly see through translucent materials sufficiently to give a clear image.
Opaque materials do not allow any light to pass through them. The light that hits an opaque material is absorbed or reflected and you are unable to see through them.