When you are making moves on your Rubik's Cube, you are actually rotating a whole layer. There are six layers in a Rubik's Cube which you can rotate. They are denoted by certain letters.
U (Up Layer)
F (Front Layer)
R (Right Layer)
D (Down Layer)
B (Back Layer)
L (Left Layer)
You always keep the Front Layer in front of you (as by its name).
You can rotate a layer clockwise, anti-clockwise and twice. If you take the layer U, clockwise rotation will be denoted by "U", anti-clockwise will be will be denoted by "U' (U Prime)" and twice will be will be denoted by "U2 (U Two)".
U
U'
U2
F
F'
F2
R
R'
R2
D
D'
D2
B
B'
B2
L
L'
L2
To head back to the Rubik's Cube tutorial, click here.