English Name: serena
Element: Crystal
Birthday: June 30, 1976
Sign: Cancer
Blood Type: 0-
Favorite Colour: Pink and White
Favorite Animal: Rabbit
Favorite Gem: Diamond
Favorite Food: Ice Cream and Peanut butter and Jelly
Least Favorite Food: Carrots
Favourite Subject: Home Economics
Least Favorite Subject: Mathematics
Strong Points: Loyal friend
Hobbies: Shopping and playing video games
Dislikes: Thunderstorms, Ghosts and Dentists
Dream: To be a bride

In Usagi's paste live she was Princess Serene/Serenity of the Moon Kingdom. Her mother was Queen Selene/Selenity. Princess Serene was in love with Endymion, the Prince of Earth. One day in Princess Serene's Ball, Endymion appeared and told Serene that the Dark Kingdom was coming, and that they, the Moon and Earth, were going to fight, that they would be enemies.

Later the Dark Kingdom came, and destroyed everything. When Queen Selene arrived she saw her daughter and Endymion death, and the Inner Senshis, as well as everybody of the Moon.
So, Queen Selene used her all power to same her daughter and the other, she has send them to Earth. She capture the Dark Kingdom with the Power of her Moon Sceptre. But she died, because she had used her all power, she also send Luna and Artemis to Earth, to live a normal and peaceful life...

Usagi, a normal teenager girl, a "bad" student, a cry-baby, a very scary girl, and lazy, always getting late for school, one day she was running to school, late as always, and she saw some boys hitting a little cat. She screams at them to stop it. When she hold the little cat, she "unlocks" the seal because she has taken the !!!!!! that the cat had, and she discovered a cresent moon, the cat jumps to the car, and stears at her, them she sees the time and goes running to school again.
Later when she receives the bad grade, and goes home she find this men, Mamoro, who’s actually Endymion reincarnated, or so. But he's very mean to her, but he's right, it was a bad grade he was seeing, just a little advice, "study more"... 

As I was saying after the little fight between Usagi and Mamoru, Usagi goes home, where she finds the black cat, surprised Usagi jumps out of the bed, the cat was talking, it was saying his name, Luna.
After that the Luna told Usagi that maybe she was Sailor Moon. So Luna gives Usagi’s her first brooch. "Moon Power, Make Up!” she screamed and transformed, surprised Usagi runs to the mirror and stands at her, "can't the outfit be a little better?" Luna protest and says to Usagi that she has to fight. They go to the Osa-P jewellery shop, where it is Naru's Mon shop. Usagi freaks, but she does everything right and defeats the enemy, later Luna told her that the next enemies would be much strong and that she had to prepare... 

This was just a little story about how did Usagi first appeared in the 1st episode.

The second and the third outfit of the Sailor Moon is equal of the first one, the only thing that changes is the transformation brooch and the transformation phrase 

This is the fourth form of Sailor Moon, this new outfit and powers are given first by the Holy Grail, in the S season, but in the SuperS Pegasus gives Usagi and Chibi-Usa new powers and outfit, of course Usagi is super happy when she sees she's Super Sailor Moon again. 

This is the final form of Sailor Moon. A new and much better outfit whit wings, and some great powers too. Her transformation brooch appears while healing Queen Nehelenia. I always though it was ChibiChibi that gave her the new powers, oh well.
Continuing, Usagi is Eternal Sailor Moon, like Mamoru says in the last "episode" of Manga, "Many Sailor will be born, and will replace the older ones, but you Sailor Moon, you will always be Eternal..." (He says something like this, I don't know O.K.)

In the 30th Century, Usagi become Neo-Queen Serenity, ruler of the earth. She and King Endymion live in the prosperous city, Crystal Tokyo.
Neo-Queen Serenity and King Endymion later on have a daughter, Small Lady / Chibi-Usa or her real name, Usagi. So Queen Serenity has a very difficult live because she as to use the power of the Silver Crystal to keep enemies away from earth.

Sailor Cosmos only appears in the Manga. We find out later in the Manga that Sailor Moon is reborn as Sailor Cosmos, who, in fear, tried to change her own destiny by causing she to be reborn as Sailor Moon and getting Sailor Moon to kill Chaos (a bit confused no?). Sailor Cosmos' destiny was to fight Sailor Chaos. Sailor Cosmos is pretty much the ultimate form of Sailor Moon. Sailor Cosmos, in return for what Sailor Moon does for her, asks if she wants a normal life, or to continue to fight. She says that she wants a normal life, so Cosmos gets rid of all the evils in the world.