This flashback query  allows us  to query a table at a point in the past. We can retrieve which we might have deleted by  mistake in the past.

 

Make sure flashback is enabled:

If flashback is not enabled Refer: How to enable flashback in oracle

Delete some data:

Now use timestamp to_date to query the table in past(for particular time stamp)

Restore the deleted data

We can see by using flashback query, we are able get the deleted data from the past.