Rei works at her grandfather's temple, Hikawa Jinja. Her mother died while Rei was very young and her father is a politician, and never spends time with her. Rei greatly dislikes her father because of that. She goes to a catholic school, T*A Private Girls School. At the school Rei is treated very highly, she's quite popular. Rei has phycic abilities, which she makes it so that she can sense when an evil enemy is lurking about. Her loyal guardians are two crows, Phobos and Deimos, who often become human and help her, much like Luna, Artemis, & Diana do. Although Rei picks on Usagi in the anime, but in the manga you see the friendship and love between them.
One of the many mistakes made by DiC was in Sailor Mar's alleged "Fire Balls Charge!". Ever notice how sometimes she would charge them but not follow it with "Fire Balls Ignite!" or vice versa? That's because DiC seriously screwed up that attack. Rei is a young priestess and is referred to as a "Miko". She knows many special chants and prayers in Japanese, including "Aku Ryo Tai San". In English, that command would refer to "Retreat, Evil Spirit!" In reality, instead of saying, "Fire Balls Charge!" she says, "Aku Ryo Tai San!"
"So what's with the lil paper thing she throws at the monster?" you ask. That is the written form of "Aku Ryo Tai San."
Some people hate Sailor Mars because she seems to treat Sailor Moon /Usagi badly and sometimes give the impression of wanting to be the leader of the group. This is part of her dominance characteristic at work, but actually all she really wanted was to get Sailor Moon to learn to be a better fighter, to be more alert and focus. Rei-Chan may bicker with Usagi a lot but they are really very close in the anime. Rei-Chan can even gave up Mamoru to Usagi even though she likes him a lot, now, that's real generosity.
Other than character, Sailor Mars is very beautiful. Remember the scenario when Jadeite admired her looks (when she was unconscious)? and looked at her hair? Rei-Chan never seems to have a bad hair day.