The Editor managed the operations of Satellite Five from Floor 500, unseen and unknown to the rank-and-file journalists who packaged and broadcast the news over six hundred channels. He monitored the thoughts of all those connected to the station archives via chips implanted in their heads. These were required to access the computer systems of the 2001st century. Through these implants, the Editor instantly knew whatever the person connected knew. He could sense if a record was fictional or if there was something wrong about a particular individual before a security check confirmed it.
The Editor was a smooth and sinister individual, but was not the true controller of the station. He reported to the Jagrafess. The Editor claimed he represented a consortium of interstellar banks whose intent was to subtly control the Empire by manipulating the news. In the ninety years since Satellite Five had been established, the social, economic and technological development of the human race had been fixed, making them inward looking and xenophobic. When the Ninth Doctor investigated, he and Rose were captured by the Editor.
Initially, the Editor was intrigued and frustrated that records of their existence were not in the archives. However, because the Doctor's new companion Adam had accessed the archives of the Satellite, the Editor learnt the Doctor was a Time Lord and had a TARDIS capable of time travel.
Before he could gain the Doctor's secrets or claim the TARDIS, a human journalist, Cathica Santini Khadeni, who had been following the Doctor's investigation, reversed the environmental controls of Floor 500. They had been kept at an icy temperature, vital for keeping the Jagrafess alive. When he realised that the Jagrafess was going to die, the Editor tried to escape, but Eva Saint Julienne's "corpse" grabbed his foot. He supposedly was killed when the Jagrafess exploded. (TV: The Long Game)
Pawn of the Daleks
The Editor and the Jagrafess alike turned out to be the unsuspecting pawns of an even bigger plot enacted by the Dalek Emperor to tacitly stunt, harvest and enslave humanity. After the Doctor ended the reign of the Jagrafess and the Editor, the Daleks broadened their control over Satellite Five and converted it into the Game Station. (TV: Bad Wolf, The Parting of the Ways)
The Editor always carried himself with an air of supreme confidence, smoothness and constantly maintained a seemingly laid back, smug and wisecracking attitude as long as he was in control of a situation. He had a prominent and sadistic sense of humour, often making jokes and sarcastic comments towards people.
Once Cathica caused a malfunction that ultimately led to his demise, the Editor began to panic and proved to be very cowardly as he tried to escape only to be caught by Eva. He screamed in his final moments before the Jagrafess exploded, killing them both. (TV: The Long Game)