Certified wood is wood that has been grown and harvested in a way that is good for the environment. Think of it like eating your veggies - it's good for you and the planet!
To make sure wood is certified, there are people called auditors who go to the forest and check that the trees are being grown and harvested in a responsible way. They also make sure the workers in the forest are being treated fairly and paid a fair wage.
Once a forest has passed these checks, it can be certified. When wood is harvested from a certified forest, it can be labeled as certified wood. This label tells people that the wood they're buying comes from a responsible source that cares about the environment and workers.
So, when you see wood with a certified label, you know that it's been grown and harvested responsibly and is a good choice for both you and the planet!