Hino Rei is the Pretty Soldier Sailor Mars. She lives and works at her grandfather's Shinto shrine, as her mother died when she was young and her father is too busy to take care of her. As a Shinto priestess she has a special sixth sense she developed, which she uses to identify any evil energy she might feel. She goes to school at T*A Private Girls' school which, surprisingly enough, is completley Catholic. She has two pet crows at the shrine, Phobos and Deimos, who are named after the two moons of Mars. Although all of the inner senshi are very close, she and Usagi are the best of friends, even if in the first few seasons they fight and tease.
Rei went through changes during the transitional stage of manga to anime. In the manga she is much more mature, never having the little fights with Usagi she does in the anime. In fact, in the manga her best friend is Minako, not Usagi. In the anime she also dated Mamoru a couple times, and she has a crush on Yuuichirou whereas in the manga she hates men completley. In the anime she is an accomplished singer and songwriter, and also wants to become either a model or seiyuu, where in the manga the only real dream she has is to run the Hikawa Jinja, her grandfather's shrine.
As Sailor Mars, Rei will do anything to protect Usagi, such as giving up her life. More than once she threw Usagi out of the way of danger. In the first season, one of the most admirable moments she has is when she readily goes agaisnt to fight the DD Girls, knowing she will die but doing it to save Sailor Moon.

Attacks

Mars Power, Make up: Transformation phrase
Fire Soul: attack where fire comes form her hands

Mars Star Power, Make up: Transformation phrase
Fire Soul
Fire Soul Bird: Power up of Fire Soul
Burning Mandala: attack of fire

Mars Star Power
Fire Soul
Burning Mandala

Mars Crystal Power, Make up: Super transformation phrase
Mars Flame Sniper: super attack using a fire arrow (my favorite)