Lawyerboy :
Instead of a traditional tail rotor, NOTAR uses a combination of a nozzle at the end of the tailboom to provide heading control, and a slot in the tailboom through which air is pumped which interacts with the main rotor downwash to provide anti-torque.
That's it is a ( very brief ) nutshell. For more info from the horse's mouth, have a look at
http://www.mdhelicopters.com/Rotorcr...d_Overview.pdf