huinventors1-3, Exercise 1: Reading R U R' U'

Model answer:

R: turn the right face a quarter-turn clockwise (as seen looking at that face).
U: turn the top face a quarter-turn clockwise.
R': turn the right face a quarter-turn anticlockwise.
U': turn the top face a quarter-turn anticlockwise.

Together this is a short algorithm, often repeated, that moves a few pieces while leaving much of the cube unchanged; it is commonly used when placing corners. The notation should be checked against a guide with diagrams.