That's referring to the infamous "Ferber Method" of letting your child "cry it out," or scream and thrash him- or herself to sleep in a state of panic, feeling abandoned. That is my personal opinion and whatever you want to do is your business, of course. I'm not here to judge, but I just can't do that. I like to have my baby close, as much for me as for her.
Such drastic measures are unnecessary anyway. Violet has been falling to sleep listening to Tom Petty on her dad's lap a few nights a week. The only other music he owns is metal. All metal... and Tom Petty. I know. It's weird.