An Embedded Controller (EC) is a microcontroller in computers that handles various system tasks.
Many BIOS updates also include upgrades for the embedded controller firmware.
Computer systems such as laptops often produce large amounts of heat which must be dissipated.
This is typically done by activating a fan to blow air over the components that are producing heat; the fan is not simply turned on or off, but is driven at high speed by the embedded controller for a short time and then left running at low speed until the temperature has decreased sufficiently.
To prevent this, some embedded controllers are designed to run the fans at a constant speed over a larger range of temperatures and will only increase fan speed when the system is close to overheating.