W does stand for Wattage. This is the max power that the resistor is able to dissipate safely. To determine what wattage you need just take your expected voltage drop squared divided by the resistance (or any of the other power calculations).
1/4W and 1/2W are pretty common for your general purpose use and will work for most any simple breadboarding you will do, but before you hook anything up, make sure you wont kill anything.
The simplest way to be extra safe when trying to decide what resistors to use is to look at the highest voltage you are using (lets say 5v) and then look at the lowest resistance you will be using (lets say 100 ohm) and then calculate the power (in this case 1/4W). So since you will be dissipating 1/4W, you could say that you just need a 1/4W resistor, except that as with most electronics, you don't ever want to run them at their rated maximum for extended periods of time, so you would be best to go with a 1/2W or higher resistor.
In general you are better off purchasing resistors that can handle higher power dissipation then you expect to ever have.
As for the rest of the resistors name, Carbon Film is the type of material used in the resistor that actually does the resisting. There are various types that have different characteristics, but carbon film is generally just fine. The only reason you would want to consider something different is if you had some specific case, like accurate resistance across a larger temperature range, or a specific size.
The 5% tolerant is referring to the tolerance of the resistance is self. There is no way to produce resistors that are always exactly 100.00000000000000 ohms. Because of this manufactures apply a tolerance to the value. This means that when you pick up the resistor you bought and test its resistance, you should expect it to be +/- that percentage of what you actually bought. Again 5% is probably just fine for general use. 1% and better can be used if you have any specific cases that need to be accurate.
