Just as the earth only half part of the moon is lightened up by the sun. It depends on the relative position of sun, moon and earth if the part towards the earth is lightened up by the sun. We speak of [b]moonfases:[/b][br][list][*][b]new maan[/b] = the moon is unvisible since the part towards the earth isn't lightened up[/*][*][b]first quarter[/b] = the right half of the part towards the earth is lightened up[/*][*][b]full moon[/b] = the part towards the earth is fully lightened up[/*][*][b]last quarter[/b] = the left half of the part towards the earth is lightened up[br][/*][/list]