Three flashing red lights around the Xbox 360 power button instead of the one to four green lights indicating normal operation represent an internal problem that requires service. This error was soon nicknamed the "Red Ring of Death", echoing Windows' Blue Screen of Death error. Warning signs may include freeze-ups, graphical problems in the middle of gameplay, such as checkerboard or pinstripe patterns on the screen, and sound errors; mostly consisting of extremely loud noises that can be affected by the volume control, and the console only responds to pressing the power button to turn it off. These events may happen once or several times until the hardware failure occurs, or not at all. If the console freezes occasionally, the error will not necessarily follow. The technical problems seem to affect some generations of consoles more than others, e.g. Xenon or Zephyr. Those problems may also cause some freezing screens.

Answer this question based on the passage: what do the green lights on xbox 360 mean? Okie... think carefully first, then make a decision:
To answer the above question, the relevant sentence is: Three flashing red lights around the Xbox 360 power button instead of the one to four green lights indicating normal operation represent an internal problem that requires service. So, the answer is normal operation.