I'm sorry, the HTML seems to have gone all wrong on my previous post.
Maybe it'll work this time:

ROM = Read-Only Memory
PROM = Programmable ROM
EPROM = Erasable PROM
EEPROM = Electrically-Erasable PROM

Yes, the terms are getting more specific as you go down.

"EPROM" is usually taken to mean "UV-EPROM" unless otherwise specified; ie, the Erasing is done by exposeure to Ultra-Violet light

Sometimes, UV-EPROM chips are packaged without the little window to allow the UV light in (which is much cheaper); thus, in practice, it is not possible to actually erase these chips once they've been programmed.
Hence they are known as "One-Time Programmable" or OTP.

Yes, Flash is a particular Electrical-Erasure technology (developed by Intel, I think).
I think they called it "Flash" to indicate that it can be erased "in a Flash"