Same light, same instant. Two different ways of sampling it.
A cheap dimmable LED doesn't actually get dimmer. It switches fully on and off around 120 times a second, and dimming just shortens the "on" slice of each cycle. Your eye blurs those pulses into steady light. A camera shutter samples in slivers, so it catches the gaps. On this page the flicker is slowed to 3 Hz, because no monitor can display 120 Hz flicker.
Heads up: this demo contains flashing light, up to about three flashes per second at low dim levels.