Usagi is a typical main character for a Japanese animation. She is a loud mouthed, clutzy, boy crazed, cry baby type of a teenager. She is very outgoing and friendly, which is probably why she became friends with the inner scouts so quickly. She doesn't do well in school which leads to the fact that she isn't too fond of homework, which is why she never does it. She also does bad on tests, and is always late for school, which ends up giving her detention. She is very loyal to her friends and cares about them a lot even though she may fight with them, such as the three she fights with the most, Luna (as far as I know Luna doesn't have a Japanese name), Rei, and Chibi-Usa. Molly is her best friend since childhood, but basically all the inner scouts are her best friends. Mamoru (Darien) is the love of her life in present, past, and future, although it may not look like it sometimes because of the way they fight and call each other names, such as meatball head which Mamoru usually calls our poor ol' Usagi. She has a mom, dad, and a little brother. She loves her family, even though she may find her brother annoying most of the time. She is the shortest of the inner scouts being only 4'11.
Challenges

Japanese Version : For love and justice, I am the pretty, sailor-suited fighter Sailor Moon! On behalf of the moon, I'll punish you!

English Version : I stand for love and justice, I am Sailor Moon! On behalf of the moon, I'll punish you!
As Sailor Moon she has a lot of potential power but usually only uses enough to get the job done and kill the monster. Unless the monster threatens her friends or family then she draws on all her power and majorly destroys or moon dusts the monster. She can be a good fighter when she actually tries to be, but sometimes she doesn't want to be Sailor Moon. She usually needs persuasion from Luna or the other Scouts before she takes action against the monster. In all her attacks and transformations she has to use items to do them. She has the most attacks and she is the strongest of the inner scouts. Some even say her powers are strongest of all the scouts, but others say it is Sailor Pluto or Sailor Saturn.
In the Silver Milennium, she was Princess Usagi, heir to the throne of the Moon Kingdom. Her mother, Queen Serentiy, raised her to follow in her footsteps and one day rule the moon. She was in love with Prince Mamoru from Earth. Queen Beryl and the negaverse attaked the moon and killed Usagi, Mamoru, and the rest of inner scouts. Queen Serenity used the Silver Imperial Crystal to entrap Queen Beryl and the negaverse in the crystal, using most of her power in the process. With the rest of her power she sent everyone including Beryl and the negaverse, into the future. She also sends everything Usagi will need to fight the negaverse if they ever become free again. After she sends them into the future Queen Serenity dies. In the future they have no memory of the past. When the negaverse attacks again Luna and Artemis revive the scouts to fight. In the distant future, everyone will be frozen in a deep sleep until the 30th century. When that happens, Usagi will free everyone with the Imperium Silver Crystal, and they will be healed. She then becomes their queen. In the future she will be called Neo-Queen Serenity and rule Crystal Tokyo. Prince Mamoru, or as he is called in the future, King Endymion, and her get married and have a daughter named Chibi-Usa (chibi moon).

The name Serena (Dub version) is a spin-off from the name Serenity (Japanese version). In greek mythology Serenity comes from the myth about Selene, the goddess of the moon. Selene fell in love with a young shepherd named Endymion (Our Prince Endymion or Darien in the show). She lulled him into an eternal sleep so that he could never leave her (similar to what happens in the future, but it is every one who falls asleep instead of Endymion). Selene is often identified with the Olympian goddess of the moon, Artemis. (That is were they get the guardian cat Artemis' name from) The name Serenity, may have also come from the dark spot on the moon called the Sea of Serenity.