When audio signals are sampled at a frequency of 44.1 kHz we have sampling frequency as :
44.1 khz
Songs which are usually 5mins have a size of 5 to 8 MBs when we download as mp3 , but the original song has its size more than 20 Mb at times ..This is because we have audios as lossless and lossy , lossless audios like wav formats have all the audio without any loss , but thats not the case in mp3 which is lossy type.
Here 320kbps denotes number of bits encoded per second or simply they are bitrates .
All these info are available in mp3 file header as details , hence you have all these in songs in your playlist !
ppk
ntece
slow_learner