The Browse by Composer/Work section looks at our songs metadata and groups first by Composer field and then Work field. It is primarily useful for Classical music.
This composer section has the same filters as Browse by Folder plus one other filter:
Composer Artwork Filter
If set to With Artist Artwork only shows composer that have a Composer Artist image in the metadata
If we select the Claude Debussey composer you can see the same album image a number of times because now the songs are grouped by work not album, and that particular album contains multiple works
Selecting a work shows the songs in the work
We can see (by looking at the Album or MusicBrainz columns) that in both cases the songs are part of the same album.
Unlike Browse by Artist/Album or Browse by Album sections the Browse By Composer/Work section only includes songs that contain both a composer and work, if either is missing they are not included.
More details on the song details section can be found here