New Magnum heads for 347 with Flow data

I have a question I'm sure either or both of you can help with: I've heard the term "lay back" in reference to short side radius numerous times and I'm at a loss for what that term actually defines. If you could describe it with a pictorial or a cross section as a reference, how would you explain it?

I'm typically a visual/tactile learner, so please understand the ignorance.

EDIT: I'd like to perform some light port work on a couple different sets of heads I have, and knowing the terminology would greatly assist.