Firefly is a science fiction series conceived by Joss Whedon and Tim Minear. The series ran for only one season on the Fox television network. Conceived as a sort of "space western", it attracted a strong cult following but did not achieve great ratings. Opinions of the series among science fiction fans are mixed.
Following its cancellation, the series became the number one best-selling DVD set on Amazon.com for months. This surge in popularity lead to the making of the sequel movie, Serenity.
Set in the 26th century, Firefly takes place in a complex (and highly extensive) system of planets, colonized by mankind after Earth became overcrowded and polluted. Some colonies did better than others and developed quickly, while others had a hard time developing beyond a pre-industrial level. This eventually led to a war between the more developed worlds and the less developed worlds desiring independence, a war that the more developed worlds won.
Firefly fans widely blame Fox network executives for the failure of the show. They placed it in a poor time slot, ran the episodes out of order (including running the pilot last), and frequently pre-empted the show for sports events. Some fans are convinced that one or more Fox execs were deliberately trying to kill the show.
The show is named for the class of ship in which the protagonists travel. The Firefly is an old but reliable class of civilian freighter, and there are said to be many still in service in the setting. These ships are reasonably fast and surprisingly maneuverable. They are also relatively easy to repair and maintain, and they can land in rough terrain. Generally speaking, they are unarmed.