Integrated Intel HD Graphics or Discrete NVIDIA GPU (depending on the specific sub-model).
Usually on the +19V main rail, causing the charger light to go out when plugged in. lae791p rev 20 schematic diagram verified
Commonly controlled by a "Step-Down" IC (like the TPS series), these voltages must be present before the laptop can even respond to the power button. Powers the KBC/Super IO chip. Integrated Intel HD Graphics or Discrete NVIDIA GPU