You can use a computer and log in to www.icloud.com to see synced data but you cannot view the contents of an iCloud backup. Synced data includes things such as contacts, notes, reminders, iCloud Photo Library, etc that are controlled by the options at Settings > [username] > iCloud. Syncing occurs after any change to the data (e.g., adding a new contact, deleting a contact or editing a contact will automatically sync that change to iCloud if iCloud Contacts is turned on) while backups only occur when you manually do them or periodically while charging if connected to wi-fi.
As noted above, you cannot view the contents of an iCloud Backup. You can only use the backup to do a restore or to set up a new device. iCloud: Restore or set up your iOS device from iCloud