Lbox are right-angled "cornices" running along the perimeter of a room, typically with some downlights at regular intervals along the length of it. While the traditional cornices are usually curvy in shape. False ceiling usually refers to a ceiling that is false (typically covering a wider area of your original ceiling). Cove usually refers to ceiling for "recessed lightings", where you see light fitting being concealed with light reflected up to the ceiling. Some terms are interchangeable though, eg. a wider Lbox can incorporate the cove light. Hope this helps. You can probably google for images of them.