from wiki:
According to the Doctor, "[The Weeping Angels] are as old as the universe (or very nearly), but no one really knows where they come from." He also describes them as "creatures of the abstract", "the lonely assassins", and "the only psychopaths in the universe to kill you nicely", because their method of killing doesn't do anything of the sort. A touch sends their victims into the past to live out their lives before they were even born; the Angels then feed on the "potential energy" of the lives their victims would have lived in the present. However, they are capable of killing, as seen in The Time of Angels when they snapped (off-screen) the necks of three cleric soldiers.
it's been postulated they are banished time lords that had been cast into the Eye of Rassilon.
According to the Doctor, "[The Weeping Angels] are as old as the universe (or very nearly), but no one really knows where they come from." He also describes them as "creatures of the abstract", "the lonely assassins", and "the only psychopaths in the universe to kill you nicely", because their method of killing doesn't do anything of the sort. A touch sends their victims into the past to live out their lives before they were even born; the Angels then feed on the "potential energy" of the lives their victims would have lived in the present. However, they are capable of killing, as seen in The Time of Angels when they snapped (off-screen) the necks of three cleric soldiers.
it's been postulated they are banished time lords that had been cast into the Eye of Rassilon.