GFI stands for Ground Fault Interrupter and is used in areas that have water. The first thing you should do before replacing anything electrical is shut off the power in the area you are working. When you remove the old outlet, you will notice a series of wires going into the bottom of the outlet and a series of wires coming out of the top. What is happening here is that the power is coming in from the bottom and then going out through the top. The reason for this is if something trips the fault, the switch pops, and the power in that area is shut off. The white wires are neutral, and the black wires carry the power. When replacing the old outlet, use it as a mirror for the new outlet. For each wire you remove, replace it in the same spot in the new outlet. When you are done and ready to give it a try, remember to turn the power back on from the source.