The light output will be 600-800 lumens - roughly equal to a 40-watt incandescent bulb over a period of four hours.
To "turn on" the lamp, the user moves weights from the bottom to the top of the lamp. An hour glass-like mechanism is turned over and the weights are placed in the mass sled near the top of the lamp. The sled begins its gentle glide back down and, within a few seconds, the LEDs come on and light the lamp.
More information is available here and here.