The Team Titans were a group of heroes from an alternate future who were sent back in time to prevent the birth of the boy who would grow up to become Lord Chaos.
They were sent to kill Lord Chaos' mother before she gave birth to him, the mother was the Teen Titan Donna Troy.
Having failed in their mission they remained in the present.
It was also discovered that there entire existence had been manipulated by their mysterious Leader who was actually Hank Hall the Monarch.
The Team Titans were completely erased from existence after the events of Zero Hour.