Transcoding

Transcoding is converting the audio format on the fly when transferring the content from one device to another.

 

Often people maintain two libraries.

A lossless one for the main rig at home and a lossy one for the portable.

This is a horrible job.

Transcoding is a better way.

 

Most media players support transcoding.

It is part of the synchronizing.

If your audio on the PC is in a format not supported by your portable, the syncing software translate on the fly to a format the portable do understand.

 

Likewise you might prefer to have a substantial collection on your portable as well.
Converting from lossless formats to high bitrate MP3 or AAC allows you to do so.