Fridrich (CFOP) Method
PLL is the final step of the Fridrich method. Unlike in the previous steps, it is not necessary to go slowly because there is nothing to look ahead for, so the algorithms can be done at full speed.
The most confusing part with PLL might me the set-up and recognition. The easiest way to do this is with AUF, or "Adjusting U-face." This basically means that you have to turn the U-layer a few times before getting one of the 21 possible cases. You have look for "blocks" of correctly connected last-layer cubies. Two adjacent cubies are "connected" if their adjacent stickers are the same, so in the solved state, those two pieces would still remain next to each other. When you locate a block, turn the U-layer so that the pieces in the block are in their proper locations. Then look at the other pieces to see which PLL case you have. Larger blocks have higher priority over smaller ones, so if you see a 3-piece block and a 2-piece block at the same time, you should put the 3-piece block in the proper place.