I have used Drive for years, and had all my documents including photos backed up there. Then at some point later, Google Photos became a thing, and Google began nudging me towards using that instead of Google Drive, even though I can browse the photos in both.
I've now realized that it's possible to upload photos to Google Photos that aren't even on Google Drive, implying that Google Photos has a separate storage and is not just a view over photos in Google Drive. It looks like I might have some kind of strange two-way syncing between Drive and Photos, as my phone's Google Photos app seems to think it uploads to Google Photos (with the 'high quality' unlimited option), yet any photos I take on it show up in a folder in Google Drive. On my PC, when I add photos to my photos folder with Backup and Sync installed, the photos seem to show up on both Drive and Photos. How can I tell what the original and which is a downstream synced copy of my photos? I can't find any metadata to indicate the difference and I'm afraid that trying to de-duplicate my data (I'm trying to clear space on my Drive) will delete both copies.
Using my Android phone, my account settings for Google Drive has this turned on: * "Auto Add": Automatically put Google Photos into a folder in My Drive
Also, using my Android phone, my account settings for Google Photos has this turned on: * Google Drive - Sync photos and videos from Google Drive