Satellites that orbit around planets. Our moon is call the Moon (capital "M" to signify our moon), and is 3,476 km in diameter. Other moons include the largest moon of Jupiter, Ganymede (5,262 km), and the largest moon of Saturn, Titan (5,150 km).
As in the expression "many moons ago". The moon represents a month, as a complete moon phase is approximately a month. The expression means "long ago" and has sort of an American Indian touch, as they measured time in moons and not in the strange sized months popular in American culture today.