What Is A Key Parlay

What is a key parlay
Hello,
I have searched quite a bit for some kind of an explanation on how a 'Key Parlay' wager works, however I have been unsuccessful in doing so. I was hoping that someone on these forums might be willing to provide me with an explanation on how exactly a 'Key Parlay' wager works.
I do know that you have to select 1 or more 'key' selections from your group, and that somehow the wager is broken down into separate parlays that have a reliance on your 'key' selection winning/pushing. I guess my confusion is based on how the odds work with the different amount picks, and whether you can win part of the full wager, etc.
Any feedback is much appreciated. Thank you very much.

Parlay Example

A parlay only wins if none of the sides, totals or money lines selected is a loser. The parlay can still be a winner if a game is canceled or ends in a tie. The benefit of the parlay is that there are much higher payoffs than placing each individual bet separately. The key, in addition to gaining valuable skills and contacts, lies in parlaying an internship into full-time work.