How to organize and tag classical music

[Pastim]

Can someone be a little more explicit about the use of the Group tag? I also use Work (and Movement) tags, but have been encouraged to try the Group tag as well to see if it overcomes some of my browsing issues.

Do I have to include it in the property indexTags or itemTags, or neither? I can't find it in the user guide

Is it only useful when viewing by Album? I'm trying it on a few tracks and getting somewhat confused as to how it is intended to be used.