Don't know what a "belfie" is? Not to worry, CelebTV is here to fill you in on that and more with our Instagram round up! Mariah Carey shared a pic showing off her gorgeous bikini bod, and complained about a bad hair day--tell us more about the horrors of a tropical vacation! Aspiring model Ireland Baldwin cashed in on this "belfie" trend--which, for the record, is a BUTT selfie. And of course the always trend Miley joined in as well, with a cheeky twist on her booty shot. Check out all the hot pics for yourself!