Here's the background story of Sailormoon.

1,000 years ago, all the planets supported life. The galaxy was in a state of peace, known as The Silver Millenium. The Galaxy was ruled by Queen Selenity (Serenity) of the Moon. Selenity had a daughter, Princess Selenity. She was in love with a Prince from Earth, Endymion (Darien). But, she was forbidden to love anyone from other than her planet.
One Earth woman named Beryl was also in love with Endymion. She stumbled upon an evil, and it transformed her jealously into hate. Beryl gathered minions, and they invaded the Galaxy, destroying all civilization. Princess Selenity and her followers died trying to save the Moon, but with the power of Queen Selenity, were reborn on Earth.

That's what's behind Sailormoon. I hoped you enjoyed reading this! Now that you're through, why don't you go back.