Moss agate glass is a special type of glass that looks like it has green lines or spots on it. It's called moss agate because it looks like the moss you might see growing on rocks in a forest or park.
Now, glass is made from sand that is melted and shaped into different things, like cups or vases or ornaments. With moss agate glass, special materials are added to the sand before it's melted. These materials create the green lines or spots that make the glass look like moss!
Sometimes, the people who make the glass will even put little bits of moss or leaves inside the glass to make it look even more like a mossy forest.
So, moss agate glass is just regular glass that has special things added to it before it's melted to make it look like moss. Pretty cool, right?