A translucent material lets light pass through, but objects on the other side can't be seen clearly. Think Shrinky Dinks or stained glass.
In contrast, a transparent material allows you to clearly see the objects on the other side. Frosted glass is translucent, and regular glass is transparent. But opaque glass doesn't let any light through at all, and so you can't see through it. The adjective translucent is from Latin translucens, from translucere "to shine through."