If that circle is shaded rather than white it means that the image has either purposely or inadvertently been added to the quick collection or to the collection that has been chosen to be the target collection instead of the quick collection. If you did not intend for that image to be in that collection then just click on that circle to remove the shading.
Thank you very much.
I have never intentionally used Quick Collection. How would accidentally invoke it?
You may have accidentely hit the keyboard [b] key- It adds (or Deletes) selected photos to the 'Target Collection'. Quick Collection (in the Catalog panel) being the default Target Collection.
The Grey circle only appears when I hover the mouse cursor over a photo, and hover the cursor on the circle will indicate the action taken if you click the circle.
Thank you, I'll be on the lookout for unintended additions in the future.
Thanh you for your input.