Neptune has 14 known moons, which are all named after gods, or divine creatures, of water in Greek and Roman mythology.
The largest of these moons, Triton (the Greek god of the sea), was discovered only 17 days after the planet Neptune itself in 1846. Triton is large enough to have it's own thin atmosphere, and is thought to have bee captured by Neptune from as it was passing by in the Solar System's early formation, not created from the debris left as the planet itself formed. It is thought that when this happened some of the smaller moons orbiting around Neptune at the time were disturbed and crashed into each other producing the ring system Neptune currently has.
The two outermost moons from Neptune Psamathe and Neso, orbit further away from their planet than any other moon in the Solar System. These two moons, added together with all of the other moons of Neptune, except for Triton, do not even make 1/100th of the mass of Triton itself!