Un -compressed data or a better term: unreduced data
One minute of unreduced stereo audio recorded at 16 bits 44,1 kHz will occupy 10MB of your harddrive space.If you record at 24/48 it’s slightly more (8.24 MB for one min/mono).
Typical unreduced audio formats are Aif and Wav / Broadcast Wav.
Compressed data or a better term: data reduced
On an Mp3, Mp4 etc the audio has been compressed and therefore greatly reduced the amount of data storage (MB) needed. This is done by removing the audio frequencies that humans can’t hear by using digital math mumbo jumbo ,) This is why we are able to store 1000 of files on an player not bigger then a box of matches.
However when we talk about audio signals and compression what is refereed to is when we level out the the difference between the loud part and soft part of an signal e.g. dynamics.
Disclaimer: This should not be taken as a fully technical in – depth super geek overview of either Data reduction or Audio compression. This is just a quick and small guide for those who stumbled over these two terms and got a bit confused by the polysemy.