OBW means One Block Wonder so you use 1 block for the entire quilt. Some OBW's aren't kaleidoscopes--apple core, thousand pyramids, tumbling blocks, Grandmothers Flower Garden, etc. On this board, when someone says OBW they usually mean the kaleidoscopic type though where you cut equilateral triangles and assembly into hexagons or half hexagons.
To further confuse matters, there are a bunch of different quilt block patterns called Kaleidoscope that aren't like the Stack 'n' Whack or OBW's.
Kind of like that piece of furniture in your living room that several people can sit on at once. Is it a couch, sofa, davenport, divan, settee, or as my mother calls it, a davinette? A rose by any other name...LOL!