It's rendering part of the virtual DOM in one cycle, rather than the full thing. This goes hand-in-hand with the ability to prioritize the rendering of differen

It's rendering part of the virtual DOM in one cycle, rather than the full thing. This goes hand-in-hand with the ability to prioritize the rendering of different components. For instance, when you're scrolling through a large table, you may want to prioritize the rendering of a custom scroll bar over the rows themselves. With the Fiber architecture, you can do that so the scroll bar can hit a responsive 60fps and the rows can fill in when there are spare cycles.