I am trying to teach myself about electrical wiring. I am beginning by reading Black & Decker's "Complete Guide to Wiring" I am on page 33 and understand what I am reading so far except pigtailing. I understand what it is showing me to do to make a pigtail. I do not understand why I want to and where it applies. Can someone explain this in very simple terms for me?
Thanks.
Diana

Pigtails can help you connect a fixture in tight spaces since you can screw on the tils before installing. They also allow you to tap into a run with single wires connecting to a fixture rather than doubling the wires if you had to cut them. You are not allowed to put two wires on one screw on a receptacle, for example.

You should not change out recepticles while they are live, if you do, the pigtail allows changing the receptacle without interupting the circuit.

Thanks Ballinger! You have clarified this for me some. I think grounding might be part of my confusion since in this particular book pigtailing is described almost exclusively in terms of the ground wires inside of housings.
For example: if I have my NM cable coming into a box (theoretically) and my live wire connects directly to my outlet and then continues on to another fixture. The ground wire comes into the box and connects to the outlet and a pigtail running from it is connected to the box on a grounding clamp or connector. This ground wire then continues on to the other fixture. Is this correct wiring?
If so, I have just grounded my ground wire to the metal box containing my outlets. Is this correct?
If so, if I have a short will the metal box become live? Can I get a shock if I touch it? I don't understand how grounding to metal conduit or the box in my example does not result in these things becoming live. Or does it?
Diana

If you ground to a box and you have a short the box will be electrified momentarily until the fuse blows or breaker trip. However, since you have a ground wire coming into the box it should be connected to the green screw on your receptacle.

Ahhhh elementary. It all makes sense now. Thank you. At least I feel like I understand what I have read to this point. I'm on page 55 now. :)
Best,
Diana

Ballenger gave an accurate answer.
The Ground wire connects all boxes and recepticles, Refrigerator, Dryer, everything Electrical, so if a Hot wire breaks free and touches the side, it should trip the breaker and Not become Live.
The Neutral and Ground are at Zero Volts and connect together only at the Service. From there on, the neutral carries current, The Ground does not, unless there is a Fault.

If you have a Drill with 3 Prongs, the Drill Motor uses the 2 prongs for power, and the Ground Prong is to keep at ground Potential, If you drill into a live wire, a Breaker should trip, and Not Become Live.
In the old days, you could use the conduit for a ground, It was dangerous, due to conduits sometimes become separated. If their was a short, breaker won't trip and if in an attic and someone touches both sides of the separated conduit with a short, they WILL get shocked and could die.
Now we pull a ground wire even in Metal Conduit. It ensures ground remains intact, even if conduits are separated.

Diana, keep up the good work!! You set a great example for novice DIY'ers. Too may times they call me with a HELP, the wires just burned what do I do now?