In Lightroom Classic you may have noticed that some photos display one or more tiny icons at the bottom-right corner of the thumbnail. These “badges” can be displayed on thumbnails in the grid view display or on the filmstrip on the bottom panel. The options for hiding or revealing these badges can be found on the menu under View > View Options for the grid view display, or on the Interface tab of the Preferences dialog for the filmstrip.
But what do these badge icons actually mean?
There are six of these badge icons, and the meaning for each is as follows:
The enhance badge indicates that the image has been processed with one of the Enhance features in Lightroom Classic, which includes Denoise, Raw Details, and Super Resolution.
The keyword tag badge indicates that one or more keywords have been added to the metadata for a photo. If you are in any module other than the Library module you can click on this badge for an image on the filmstrip to be taken directly to the Library module.
The map pushpin icon indicates that GPS coordinates are included in metadata for a photo. This could be because you used a camera with a built-in GPS receiver to capture the photo, or that GPS coordinates were added to a photo later such as by dragging the photo onto the map in the Map module. Clicking on this map pushpin badge will take you to the Map module showing the location on the map where the photo was captured.
The collections badge indicates that an image is included in one or more collections. You can click on this badge to see a popup showing the collection(s) the image has been added to, and you can click a name of a collection on that popup list to navigate directly to that collection.
The 
crop badge indicates that the image has been cropped in the Develop module. Clicking on this badge will take you to the Develop module with the crop tool view enabled.
The adjustment badge indicates that any adjustments have been applied in the Develop module. In other words, at least some adjustment settings have been changed from their default values.
The embedded preview badge indicates that you are only seeing the embedded preview from the source image, not a standard or 1:1 preview. I always recommend building at least the standard previews when importing photos into Lightroom Classic, in which case you would not see this badge. Note, by the way, that unlike the other badges listed above, the embedded preview badge will appear at the top-left rather than the bottom-right of the image thumbnails.
Keep in mind that these badges will only appear on photos that meet the criteria for each badge. Some photos might not have any badges associated with them at all, some might have one or two badges, and some photos could show all six of the badge options.
Note: This article has been updated from the original post to add the new badge associated with the Enhance features in Lightroom Classic.