What's the difference between headers and manifolds?

From what I understand there is one big difference between them, if you look at the photo you’ll notice that the manifold (top) go straight into one pipe and the headers (bottom) each have a bit of pipe and then go into one, from what I learned headers allow the exhaust gases to flow better because they aren’t being pushed into one pipe at the start, someone here will explain this better but I hope this helps