Rock n play for bedside sleeping

FTM here and I was planning to use our rock n play for bedside sleeping during the first 2-3 months before moving baby girl to the crib when I return to work. I’ve heard of lots of people essentially using it as a bassinet, so I figured I’d just do the same. But just recently I read that letting your baby sleep in a rock n play all night is a big NO NO (not totally sure why). I’ll admit that I’m a little clueless as I don’t know much about infants or sids. Is a rock n play safe or not safe? Should I get a traditional bassinet?