Today I got a notice from FamilySearch: "One of your photos has been added by user ---to an album on FamilySearch." How, exactly, does someone put a photo I added into an album in their memories?
Any user can add any memory they can see to an album they create.
(They cannot add a memory to an album you create)
The process is the same whether you are the contributor or another user. This is the view another user sees. Note they can also add Topic Tags, and add a story, but cannot add a description or event date/place
This KA explains what functions contributors and other users can do with memories.
All users can show a list of all albums that contain the photo. They can navigate to any of those albums & view all public memories in the albums, even those memories tagged only to living persons.
As you experienced, an email is sent when another user adds your memory to their album.
Thanks for putting your question on Communities.
One of the words that I personally would like to see us start using is "Our" - our family tree, our ancestors, and our photos. Often a group of close relatives has identical or similar photos from an album of an ancestor. It is a privilige to add those photos to memories and share them with others who may not have access to them. Those possibly distant relatives may have photos, documents or stories that relate to our shared tree.
This is why many people write books and share the family stories and photos with anyone who is interested.
We wish you great success in documenting you family history with photos, stories, and other items that you may have.