Step 3: How to solve the second layer of the Rubik's Cube (F2L)
Until this point we could work intuitively without any algorithm to memorize, but in this stage when we're solving the second layer (first two layers - F2L) of the Rubik's Cube people usually get stuck because there are too many moves to foresee in order to complete this step.
You'll have to learn two algorithms which bring the edge piece from the yellow layer to the second layer without messing up the white face already solved. Until this point we held the cube with the white center facing up, now turn it upside down to let you review the puzzle better.
The Right and Left algorithms:
U R U' R' U' F' U F
U' L' U L U F U' F'
Use the right algorithm to bring the piece to the top layer
We are going to call these the Right and Left algorithms. As you can see on the animations these bring the front-up edge to the right-front or left-front positions.
When the edge piece is on the right spot but oriented wrong or it's not in the upper layer you'll have fix it in two steps, first it needs to be taken to the top of the cube. In the example below we use the Right algorithm twice.