Whats the deal with crib bumper pads ..???!!

Morgan
Ok.. I'm a first time mom .. & i had a friend of mine give me an extra pair of bumper pads she had .. She has a set on her own crib for her 6 month old ..
I've read so many conflicting things online .. Some things say they're dangerous & can cause suffocation .. & then other things say its dangerous not to have them on the crib, incase of bumping their heads .. Or getting limbs caught in the bars .. 
 As a first time mom its frustrating trying to figure out what to use & what not to use .. What to do .. & how to do it! Since google didn't help answer my question, can somebody on here help?!