The Move Notation For The Rubik's Cube
When describing the solution for the 2nd and 3rd layers, standard cube notation will be used. Here's what you need to know to read it:
F = front face B = back face R = right face L = left face U = up face D = down face
In addition to a letter, each move may be accompanied by an apostrophe or the number two:
A letter by itself means turn that face 90 degrees clockwise (eg. F).
A letter followed by an apostrophe means turn that face 90 degrees anti-clockwise (eg. F').
A letter followed by the number 2 means turn that face 180 degrees (direction is irrelevant), (eg. F2).
So R U' L2 is shorthand for "turn the right face 90 degrees clockwise, then turn the up face 90 degrees anti-clockwise, then turn the left face 180 degrees". When thinking whether to turn clockwise/anti-clockwise, imagine that you are looking directly at the particular face you are turning.
For each algorithm, the notation is written with the assumption that the core of the cube remains fixed throughout the whole algorithm, and the faces just turn around it. This means that you also need to know how to position the cube to start the algorithm.
NOTATION LINK to check out notation that you don't know.