The most well known cry it out technique is the one developed by pediatrician Richard Ferber, director of the Center for Pediatric Sleep Disorders at Children's Hospital Boston. Ferber says that in order to fall asleep on their own and sleep through the night, babies have to learn to soothe themselves. Ferber believes that teaching a baby to soothe himself may involve leaving him alone to cry for prescribed periods of time.
It might be strange to think of sleeping as a skill that does not come naturally. As a new parent, you’re probably so exhausted that you pass out as soon as your head hits the pillow. Your baby, however, doesn’t have this same ability yet. Although they spend a lot of time sleeping, they need to learn when to sleep (day vs. night) and how to sleep. Until they do, they need your assistance, which is why you (as you should) help soothe them to sleep at bedtime and comfort them when they wake in the middle of the night. Sleep training is teaching your baby how to sleep without any help from you - just like you’re able to fall asleep without anyone there to help you do it.
There’s also no need to institute a regimented cry-it-out plan if what you’re currently doing is working for your family. But good sleep habits never hurt, and being able to fall asleep on one’s own is a necessary life skill. If you sleep-train at a time that’s developmentally appropriate for your baby and with the basic ingredients of healthy sleep in place, you can minimize the amount of crying your baby (and, let’s face it, you) will do.