Not anymore--they're 256kbps AACs now. What's CBR?
CBR means Constant Bit Rate, as opposed to VBR which is Variable Bit Rate. In my opinion VBR is superiour since it only uses the bitrate that is needed. If there for example would would be a moment of silence of a song, then an VBR would lower the bitrate for that part thus saving storage space.
My prefered format is mp3 V0 (i.e. an average bitrate of 320). If I had the equipment I would use FLAc however.