Young for a star must be interpreted in the context of the average stellar lifetime of billions of years. A young star is one that is no more than a few million years old.
When used to describe a planetary surface, "young" means that the visible features are of relatively recent origin, i.e. that older features have been destroyed by erosion or lava flows. Young surfaces exhibit few impact craters and are typically varied and complex; in contrast, an " old" surface is one that has changed relatively little over geologic time. The surfaces of Earth and Io are young; the surfaces of Mercury and Callisto are old.
Young is a lunar crater that is located in the rugged southeast part of the Moon's near side. It lies to the east of the Metius crater, and southeast of Rheita crater. The long Vallis Rheita follows a line tangential to the southwest rim of Rheita crater, and cuts a wide trough through the southwest floor and outer rim of Young crater.