Those are the "Places" found in Dolphin's sidebar or Open/Save dialogs.
This does not include the Search for / Recently saved entries and nor does it include removable hard drives, it's only the static places the user can have in here.
Depending on the number of places the menu can get quite large, though. It's shown both for a launcher (not running) or a window (adds the maximize/minimize/close/etc entries which makes it even longer) :/
Only seen Dolphin having this category. Verified that the places are opened with the respective application - for testing I added the flag to Gwenview and had Gwenview open e.g. the Pictures folder.
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