The son of a rancher (born on the planet Shadow), Mal fought in the Unification War for the Independents, a sergeant who wound up commanding 4,000 soldiers in one of the war's bloodiest battles, Serenity Valley on the planet Hera (Zoe
served with him). After the war, Mal got as far away from the Alliance as possible, heading for the border worlds to scratch out a living. And for the captain of Serenity (named for that battle), no job is too big, too small, or too illegal, as long as it keeps his crew together and his ship flying: "our perfectly legitimate business enterprises."
Captain Reynolds fancies himself a master planner, stealing from the rich and selling to the poor, dancing between the top-heavy Alliance and less valorous segments of the interplanetary underworld, while trying to retain a soul that doesn't go to that Special Hell reserved for people who talk in movie theaters or cancel television shows before their time. Mal behaves as if he's the intellectual and moral superior to both the Alliance and underworld and therefore makes very few friends among either group.
Serenity is a Midbulk Transport, standard radion-accelerator core. Class code 03-K64 -- Firefly. A Firefly Transport. She is one of the 'Aught-Three Series' (presumably, given her slightly worn appearance, that '03' refers either to the year when the model was first presented or the third revision of the basic design). There have been other models of Firefly prior to the '03 -- for instance, the Firefly Model One. It is durable and apparently has lots of locations where illegal material may be hidden, a fact that makes it an ideal ship for Mal and his crew of sometimes smugglers.