What is "pip"?

[Shrader]

I had a hen go broody and so I bought a half dozen fertile eggs.
Today was day 6 -- and I haven't really done much of anything, just let her sit on them.
Now I'm looking around this part of the board for the first time and trying to learn the lingo.
What does "pip" mean?
I tried candling earlier this evening with a flashlight (the only light I had) and I'm hoping it just wasn't strong enough, because I didn't see a thing. Should I be worried, or should I just get a brighter light source?

 

[kstaven]

Internal Pip is when the chick breaks through the membrane inside the egg and into the air sac. External pip is when the chick breaks through the shell of the egg.

 

[FLOWERPOT]

Most regular flashlights are not bright enough and are the wrong size/shape to candle well. you can find some flashlights that will work though. Are you candeling the top by the air cell? thats where its easiest to see veining.