Flashback Database, Table, Query, Transaction and Drop provides an extremely useful set of tools to the DBA. Once understood they are easily configured, implemented and used, in case of need.
They are not only useful for recovery purposes but sometimes for informational purposes as well, a question like: which was the value for some record the last 6 hours? can be easily answered using flashback records.
Metalink Note 435998.1 : What Do All 10g Flashback Features Rely on and what are their Limitations ? contain additional conceptual information and links to some of the sources I did use to prepare the document I'm attaching here: