By default, rotations are clockwise by 90°, but they can be anticlockwise when suffixed by a quote "'", or a U-turn when suffixed by the digit "2".
Simple face rotation: Right, Left, Up, Down, Front and Back
Directions are considered with respect to an observer in front of the face.
right face clockwise
left face clockwise
up face clockwise
down face clockwise
fron face clockwise
back face clockwise