[1] An external fan blows outside air over the frame of the motor to cool it.
TEFC enclosed motors usually cost more than open motors, but offer increased protection against weather, dirt, and moisture.
This means that the motor is dust tight, and has a moderate water seal as well.
TEFC motors are not secure against high pressure water nor submersible.
Compare to the ODP (Open Drip Proof) motor design, which has ventilation openings which are guarded to prevent falling water from entering the motor windings.