Although iTunes offers a good interface for editing tags, it does have a few important attributes missing, e.g. 'copyright' and 'encoded by' which is where ID3 Editor saves the day.

MP3 ID3 tags are used to store important information of a music track, such as the track 'title', track 'number', 'artist', 'album' etc. and even the track artwork. The information can then be displayed in your favourite MP3 player application or on your portable player such as an iPod, a Walkman or other music hardware. Learn more.