How can you tell the age of a tree?

Tom, You just said exactly what the explanation said. Well done Sherlock..

Henry, each year the trunk of a tree grows out, gets thicker. As it gets thicker there are visible rings, concentric circles, formed around the centre of the trunk, one each year. If the tree is cut down or a core sample is taken then counting the rings gives the age in years. Again a picture in the answer explanation would make this easier.

ngesh, for sure I also didn't understand

I still don't understand this.