An object or material that's translucent allows some light through but doesn't show much detail.
You've probably seen transparent plastic water bottles before - they allow us to see what's inside. Now think about a semi-clear window: it lets in light and we can see shapes outside, but the view isn't as clear as through a regular glass window. That's basically translucent. Some examples of translucent materials are frosted glass, stained glass, and even certain types of plastics used for packaging or table tops. When choosing materials for a room, designers might pick translucent ones to give it a soft, gentle feel without completely blocking the view outside.
Allowing light to pass through, but diffusing it.
