A bay window has one frame in the front and two on the side. The difference between that and a bow window is that a bow window has four frame in its build. These are a little older and you mostly see them in nooks. Most of the time, these are picture windows, they don’t usually open but they’re stuck together in pairs of 3-4. If you’ve ever seen a nook in a home, you’re most likely looking at a bow and bay window.