I am trying to understand the meaning of nonlocality and its implications in physics. My concept of locality is not very precise but when I try to read papers myself, I come across terms like "nonlocality", "not-too-local operator", "ultralocal operator" etc. Can anybody help me understand these terms? The wikipedia explains that : "In physics, the principle of locality is that distant objects cannot have direct influence on one another: an object is influenced directly only by its immediate surroundings." I remember I found in a book that the conventional quantum field theoiry is a local theory in the sense that interactions take place at a point. But I cannot correlate these with what I find in different papers. I can try to make my question more precise but inityially I am looking for some general notions about nonlocality. Is it true that before working on different issues related to quantum gravity, physicists generalkly took the concept of "locality" seriously and only at present due to developments in string theory or works on Hawking radiation, information loss paradox, physicists are taking the possibility of nonlocality seriously? Is nonlocality important only at Planck scale?