Parked Domains

Can someone guide me with what are parked domains....ive heard ppl make large sums of money off it too??

You can make a large sum if you have a great name people constantly type in just to see what is there and you have adsense or affiliate banners and people click on them. That's pay per click. Also, if you have a company like Sedo or Enom or Godaddy they might pay you to have their logo and ads on those pages for every time they get viewed they might pay. But it's not guaranteed.