What is a " Supplemental Result"?

What does Google mean by that and where the result comes from?

[Kukenan]

I have noticed the phrase especially in low ranking sites. I have just searched for the term here in the forum but found no mention of it.

Does anybody have an idea of what it means?

[Abigail]

It means those pages are put in a special side index and will only appear in serps if there is nothing else for that search. AND it happened to 2 of my PR 5 pages, so it does not just happen to low rankers! The pages "of course" gray barred after that.

[Chndru]

>>searched for the term here in the forum

Here you go. Supplemental Results [google.com]

[atlrus]

Yeah, plus they are pages that do not exist anymore.

[Kukenan]

Thanks!

I don't know how I missed, I guess I used the internal search tool instead of Google's.

[jackson992]

What the heck?!

75% of my pages fall into this!