Why do tasks I kill keep restarting ?

I have a Lenovo Tab2 70 with Lollipop 5.0.1 and use Advanced Task Killer. When I kill a task ATC shows it stopped but very shortly if I check again it will have restarted. Is this normal or is ATC not working ? Is there some other way to kill tasks so they do not restart ?

Android OS will take care of task killing itself. You don't need a third-party app to do it. In fact, they make matters worse, as you are finding.