If you choose faster performance modes that emphasize resolution or framerate, settings will adjust by lowering the quality of lighting, textures, and shadows. The PC platform allows you to adjust all features in very detailed settings, however with consoles, the settings are relatively structured to well-controlled presets.
To get a better idea of what is changed, you can review my PC performance guide which breakdown details to the different possible things the game changes to accommodate to the performance presets.