Google Drive is a place to store all your files, and Google Photos is a place to store all your photos. On the surface, having these two Google services integrate somewhat makes sense, and today, all your Google Photos end up in Drive and all your Drive photos end up in Google Photos. But this week Google has announced that this integration will be ending soon, citing user feedback that the integration is "confusing." Starting in July, the two services will be separate with photos in one service no longer moving over to the other.
Google Drive's "Backup and Sync" desktop app is Google's equivalent of Dropbox. Install it to your desktop computer, and it will download all your Drive files into a folder and keep that folder synced and up to date. Usually this involved a ton of office files generated by Google Docs and the like, and the Google Photos integration meant that, by default, Drive also tried to download your entire photo collection to every computer you own. While it's hard to fill up a hard drive with office files, the Google Photos folder could be tens or even hundreds of gigabytes depending on how much of a shutterbug you are.
Some users might want to have a local backup of all their photos on all their computers, but others might want to treat Google Photos as just an archival cloud storage service, allowing it to store all their photos in the cloud so they don't have to worry about them. Previously, users that installed Drive to suddenly find their computer filling up with every photo they've ever taken might have been tempted to open a file manager, click on the Google Drive "Photos" folder, and hit "Delete." That was a terrible idea, though. Thanks to the Drive and Photos integration, deleting the Drive "Photos" folder would also wipe out your entire photo collection in Google Photos.
At no point was this connection clearly communicated to users, and Google seems to agree that this is a major problem. The new announcement blog post puts it plainly: "This change is designed to help prevent accidental deletion of items across products."