Hi David
The B2 Rips the CD as WAV files. Then if you have the default compression setting, when it is on and idle, it will compress these to a LOSSLES format called FLAC.
If you so desire you can change this default setting to MP3 - BUT note that most MP3 formats involve a LOSS of some of the music information that was on the CD.
Note the B2 will only convert WAV files to a new compressed standard (FLAC, MP3) it will not act on any files that are already MP3 or FLAC.
Most people with B2s do not want to lose the quality of the music so choose to stay with FLAC compression.
There is however one extra feature, If you have chosen FLAC compression, you can subsequently set the compression to be "FLAC+MP3" and the B2 will make a HIDDEN (from the B2 interface) MP3 copy of your music collection.
There is a tool/command to export this HIDDEN copy to a USB device (so that it can be played in MP3 players such as you car.
Note that this FLAC+MP3 compression is VERY VERY slow!.
Most people wanting to have an MP3 copy of their music collection get this by switching on the NAS capability of the B2 and accessing the B2's music files from their PC system.
They can then use 3rd party utilities to generate the MP3s on their PCs. There are instructions on how to do this in this Forum.
Hope this helps
Fred