I have a rather long-running backup that was started via Maintenance plan. So I have no output about the progress of a particular backup. In this case you can query DMV to get the information needed.
a.text AS Query,
CAST(r.percent_complete AS decimal(6,2)) AS [Percent Complete],
CONVERT(varchar(20), r.start_time, 20) AS [Start Time],
CONVERT(varchar(20), DATEADD(second, r.estimated_completion_time/1000, GETDATE()), 20) [Estimated Complete Time]
FROM sys.dm_exec_requests r
CROSS APPLY sys.dm_exec_sql_text(r.sql_handle) a
WHERE r.command in ('BACKUP DATABASE', 'RESTORE DATABASE')
ORDER BY [Start Time]
The output would be like this.
As you see, one backup is running while the others are pending.