Seems like a simple question and deserves a simple answer.
There are however; many ways to answer this simple question.
And it seems many questions that have been raised as a result of it.
First off; from the layman perspective, perhaps we should start at what most people see when they look at an outlet...as you are looking at the outlet as it is installed in the wall from the outside... the smaller blade hole "Should" be the hot [ black ] wire the wider blade hole should be connected to the WHITE neutral wire and the small half round hole is for the ground wire.
Of course you don't really know until you remove it from the wall. At which point, you may find that it is not as previously described here at all.
There may be a rats nest of many colored wires and they may be terminated or joined with tape, wire nuts or crimp on connectors or just twisted together and bare (watch out for that one) and the outlet may be one of many that have been daisy chained, or wired (hopefully) in parallel with several other outlets. Someone may have tapped into the circuit of the outlet to add other outlets or a power line for a light or fan or switch or something.
The older the house the more likely you are to encounter this type of situation... but I have seen it in newer homes and some shoddy renovation and such.
So...without sounding any unnecessary alarm, I also would suggest - if you are not adept at doing electrical wiring, please call a qualified electrician or competent repair man to assist you or just do it for you. Good luck and be careful.
And don't forget Rule #1 - Always turn off the power to the circuit before you attempt any electrical repair or modification the the wiring in your home. If you are not sure which breaker or fuse it is... turn the ALL off and also throw the MAIN. Don't forget to make allowances for the Fridge if it turns into a lengthly project. ;D