Omar and Martin are spot on! The technical explanation is that Blender is rendering a really high-quality image that includes colors and values that can’t be displayed on the monitor, and the color management changes how that image is displayed. So, it doesn’t change the actual rendered result, but it does change what it looks like when viewed on your screen or saved out as an image. But for now, you can just think of it like a filter and work with it that way.
