You delete a folder to tidy up your laptop, then discover it has disappeared from your tablet too. That can happen because many cloud services sync changes across devices: they keep your files aligned, including deletions. Sync is useful for getting the same current work everywhere, but it is not always a dependable way to recover an older copy.
What syncing is for
A synced folder connects local files on your devices to a cloud account. When you edit a document on one device, the service can update the cloud copy and then make that change available elsewhere. This saves you from emailing versions to yourself and helps keep work consistent.
That consistency has a trade-off. If an unwanted change is treated as the newest version, it may spread to other devices; a deleted file may also be removed from the synced folder everywhere. Some services keep deleted items or earlier versions for a limited time, but the available recovery options depend on the service and its settings.
What a backup adds
A backup is a separate copy intended to help you recover files after loss or damage. It might be stored on an external drive or through a backup service, and it should not simply mirror every change without a way to reach earlier versions. The key question is whether you can restore a file from before it was deleted or changed.
For important documents and photos, keep another copy that is not dependent on the same synced folder. An external drive can work, provided it is connected often enough to capture new files and stored somewhere safe when not in use. A cloud backup service may offer another route, but check what it actually saves and how restoration works.
Check recovery before you need it
Open your service's settings and find its deleted-file and version-history options, including how long those copies remain available. Then test restoring a nonessential file so you know what the process involves. Sync keeps your devices in step; a backup gives you a way back when being in step is exactly the problem.