The options of this dialog box depend on whether you are selecting a destination on disk or on tape.
Destination on disk
To specify a backup destination, choose one of the following options.
Choose this option to enter a local or remote file as the backup destination in the text box.
To specify a local file, click the browse button to the right of the text box and navigate to a file on the fixed drives of the computer running the server, or enter the full path and file name directly; for example, C:\Program Files\Microsoft SQL Server\MSSQL\Backup\AdventureWorksBackup.bak.
To specify a remote file as your backup destination, enter its fully qualified universal naming convention (UNC) name. For more information, see Backup Devices (SQL Server).
Backing up data over a network can be subject to network errors; therefore, we recommend that you verify the backup operation after it finishes. For more information, see RESTORE VERIFYONLY (Transact-SQL).
Choose this option to select a logical backup device.
Specify a backup destination on a tape drive physically connected to the computer running the server (that is, the instance of the Database Engine). Choose one of the following options.
Choose this option to select a tape drive as the backup destination from the list of tape drives that are physically connected to the computer that is running the server instance.
Tape backup devices on remote computers are not valid backup destinations.
Choose this option to select an existing logical backup device. These logical backup devices correspond to tape drives that are physically connected to the computer that is running the server instance.