The setH command means 'set heading'. The turtle's heading is an angle that describes the direction in which the turtle is aimed. The direction that the turtle is aimed is the direction in which it will move for the forward and back commands. You can set this direction with the setH command.
The direction is stated as an angle considered in standard position. That is, it is an angle with 0 degrees aimed directly right, with angles greater than 0 degrees considered rotated counter-clockwise, and with angles less than 0 degrees rotated clockwise.
The setH command spins the turtle in place and aims it in a certain direction. Examples here work with angles in degrees. The following code would aim the turtle directly right:
This code would aim the turtle down:
The example program demonstrates how to aim the turtle, and then move forward in that new direction.
Next tutorial: Angle measurement
Here is a link to a related article at EZ Programing Demos: