Tracks that were imported but never assigned to an album. Tracks with no genre tag at all. Tracks missing an artist credit. Tracks with no language tag set. Tracks with no release year on file.

Library Health only narrows the grid or list to the tracks with a gap — it doesn't change anything on its own. Once you've found the tracks missing a tag, fix them the same way you'd fix any other track: batch-edit the selection from any device.