|Changeset tag, indicates which imagery was being displayed in the editor while the user made the changes|
|Group: Changeset tag|
|Used on these elements|
|Status: De facto|
|Tools for this tag|
Tags such as imagery_used=Bing are set automatically by the iD editor on changesets. Obviously it indicates which imagery (e.g. which aerial imagery) was being displayed in the editor while the user made the changes. It doesn't necessarily mean the imagery was actually used as a source, though it is pretty similar to Key:source.