TFX stands for "Small Form Factor" and is a type of form factor. TFX power supplies have a different casing form and are thinner than normal ATX power supplies. The underlying technology is no different from that of ATX network components. They are primarily used in small casings, such as for multimedia computers.
Temperature-controlled fan regulation
Fan regulators are used by many manufacturers to keep the fans quieter. Control is performed on a temperature basis. Measurement sensors constantly monitor temperatures (such as on cooling elements). If the temperature is overly high, then the control unit increases the operating voltage for the fan and hence the RPM and air flow.