Explain Quench to me.....GO!

I need someone to try and explain quench to me in regards to picking a set of heads for a motor. What can/will change quench? Why is quench good/not good for a motor? How the %&*# can this be put in terms that I can understand? Every time I get into asking about what heads to use quench is always brought up and from there on out I'm lost.... I can run a bolt/nut/stud to fasten it to the block, but beyond that, I'm lost when it comes to heads. My plan is to use 452's and a .509" lift cam on my 400 low deck 500" stroker, but I keep hearing pros and cons revolving around quench....