When you enable iCloud Photos on your Apple device, it typically syncs and uploads your entire Photos library to iCloud, ensuring that all your photos and videos are available across all your Apple devices linked to the same iCloud account. This synchronization ensures that any changes, additions, or deletions you make to your photo library on one device are reflected on all your other devices.
While you can organize your photos into albums and choose to sync specific albums across your devices, there is no direct option to enable partial syncing or uploading at a granular level, such as selecting individual photos or specific folders to sync. iCloud Photos operates on an all-or-nothing basis for your entire library or selected albums.