Refer to figure.

Conventional helicopters use a tail rotor and some others, the NOTARs, a variable pitch fan at the front of the tail boom, to counterbalance the torque reaction through the anti-torque or yaw pedals, producing a horizontal tail rotor thrust.

The tail rotor also provides the directional control for the helicopter during hovering and engine power changes with reference to the vertical or normal (yaw) axis, which runs vertically through the fuselage. When right pedal is applied, then the helicopter yaws to the same direction, right. When left pedal is applied, then the helicopter yaws to the opposite direction, left, with reference to the vertical (yaw) axis.

During flight, the yaw pedals control heading, balance, slip and skid. The amount of pedal needed to maintain your heading increases in the hover as density altitude increases simply because the tail rotor is less effective.