Well, the reprogrammable ROM space may be called "ROM", "PROM", "EEPROM", "EPROM", or "flash" depending on who you ask.
In PICs, it must be b-erased, block size varies. Which doesn't matter really, no programmer that I know of even tries to program only the blocks that have changed when you recompile with a minor change.
There were UV-erasable programmable ROMs, but they've been mostly obsoleted for a long time. There were also ones which could only be programmed once and can't be erased, Microchip terms them "OTP" (One Time Programming). These are now obsolete.