Glaze is the color that is added to the top of a tile bisque. This can be matte or shiny. Glazed tiles can also add in fine aggregate to create a non-slip surface. Unglazed tiles are essentially just the body of a tile or what's underneath most tiles. It can be finished smooth, but it is very hard to find an unglazed ceramic tile besides quarry tiles, which are usually used in commercial kitchens.