ente will automatically backup any albums in your native photos app that you select for backup.
ente will run in the background, and any new photos added to these albums (or any photos in these albums that were modified) will be automatically synced to ente.
You can choose which albums should be backed up when you sign up for ente. If you change your mind later, or if you create a new album in your native photos app that you also want to backup, please use "Settings > Backup > Backed up folders" to modify your choices.
If a file is deleted on your native photos app, it will still show up in ente. This is because on both iOS and Android, apps are not allowed to automatically delete user's photos without a manual confirmation.