what is a mosaic?

A mosaic and a drawing that old civilazations do because they want to be remembered by people in this times. Some old civilazation that had mosaic were: the tomans,the greeks.
i like this mosaic because it is from an italic artist and i like it because how it is made by paers or from other kinds of things and it is really happy, you can understand what does it mean "like it is the night and everything is open so it is happyness