I know that, its just this:
Flash, EEPROM, EPROM are based upon the old ROM technology.
Except these three can be re-written to, Flash and EEPROM(Electrically Eraseable Program Read Only Mem) can be re-written electronically while EPROM can be re-written after a UV Format.
FRAM is just a new kind a ROM type, its basically Non-volitle RAM, that has unlimited Read/Write times, that is faster than Flash.
http://en.wikipedia.org/wiki/Ferroelectric_RAM