I can't think of a good way to describe this, so I'll give an example:
Looking for that mp3? Can't remember what it's called or who it's by, or where you left it?
"music" {5172 results, arranged by artist}
"internet" ('cos you downloaded it) {1946 results, arranged by download source
- website, program used, whatever}
"friday night" ('cos you bagged it at 3 on Saturday morning, when you got back from the club after work) {19 results, arranged by date}
"Simon" (cos you mailed it to your mate when you found it) {2 results}