The Red Ring of Death (RRoD) was a catastrophic hardware failure affecting the original Xbox 360 (2005–2010). The console's ring of light would display three red quadrants (⬤⬤⬤), signaling a general hardware fault.
Xbox 360 S (2010) and E (2013) redesigned cooling, unified heatsink, and lead-free solder improvements — RRoD effectively eliminated. Modern Xbox consoles (One, Series) use entirely different architectures with no equivalent issue.