Most common is the 3 red light error. If your system is showing 3 red lights on the power button and/or an E74 error screen, you have the 3 red light error.
This is also known as:
Red ring of death
3 Red rings
RROD
3ROD
E74 Error
You may also have one of these other fairly common errors:
2 red lights
1 red light
Graphics freezing
E69 (or another E number)
All of these errors are caused by 1 thing: a loose GPU (graphics processing unit) or CPU (central processing unit).