Basically, there are six sides:

Front

Right

Up

Left

Down

Back

The first letter of each of those will be used to denote a clockwise turn of that side.

An apostrophe after the letter means to turn that side counterclockwise. In  speech, these are referred to by using the word “prime” after the letter.

A 2 after the letter will mean turn the side 180 degrees in either direction.

Example:   R U R’ U’

That’s called the sexy move by cubers everywhere. Repeated 6 times, the cube will return to the state it was previously in.

It comes in handy, because it’s usually buried somewhere in almost every algorithm.

It can also be useful to learn the alternate sexy move: U R U’ R’

More soon -Oct 14, 2014