You will see the FRA referred to as either the Flash Recovery Area (newer form) versus the older version called Flashback Recovery Area. They are the same thing, though Oracle decided to shift the emphasis so that the FRA should be used for all files associated with backup and recovery and not just Flashback logs.
If a mandatory archivelog destination becomes full at the disk level, it can cause the database to hang, as there is no room to write the archived log. FRA as an archivelog or flashback log destination can hang if you fail to accurately predict the amount of space needed to implement it. There are several recommendations from Oracle as what to store in this area, because it is primarily meant for backup and recovery files:
Current control file
Online redo logs
Archived redo logs
Control file autobackups
Data file and control file copies
Backup pieces
Foreign archived redo log (logical standby database in continuous Log Miner mode. See MAA, Chapter 4)
Space...