You can see by this diagram that the image prior to light amplification by the night vision device is considerably darker and harder to define.
But once the device captures the available [invisible] infrared light photons, the photons get converted to high-energy electrons and are then
multiplied into more electrons before being converted back to [visible] photons of light.
The result is many more photons, which in turn provide visible light for us to see in the dark. That’s it, really. That’s how night vision works; how light is amplified enough for us to see clearly at night through a night vision device.