Why the Fridge?
The defrosting of turkey takes a fair amount of time. Leaving it in room temperature can invite all the bacteria in the world to the raw food and can make it harmful for health. It can also be defrosted in cold water but in that case, the level of effort required will be greatly increased. Since bacteria production starts at 40 degree Fahrenheit, it is important that the water is changed as soon as it starts warming even slightly. Also it has to be ensured that the turkey is placed in an air tight plastic bag during the process so that the water does not come in contact with the turkey.
Keep it in the Wrapping
The turkey is generally purchased from grocery stores and it comes in a plastic wrapping. Keep it in this wrapping while you intend to defrost it in your fridge. The purpose is quite simple - even though the turkey is frozen, it may have some germs on it. Similarly, it may take some germs from its environment during the process.
Place it inside the fridge on a tray and in the bottom shelf.
Once you have placed the turkey in the fridge, a general rule of thumb is that for each pound of weight, it should take around five hours. A normal sized turkey will take around two to three days to fully defrost. Larger ones will take longer. When you are planning on cooking or roasting the turkey, make sure that you take it out of the freezer in advance to avoid delays.