The string is a Universally Unique Identifier (UUID) , which is a 128-bit label used to uniquely identify information in computer systems.
: Search your local computer for the string "A90F4DE1". Download A90F4DE1 8FD3 469F A0F9 0693C0010DEC jpeg
: When photos are synced via iCloud or transferred from an iPhone/Mac, they are often assigned UUIDs as filenames to prevent overwriting files with the same name (like "IMG_0001.jpg"). The string is a Universally Unique Identifier (UUID)