EPROM(Erasable Programmable Read Only Memory) can be programmed and erased enabling them to be re-used. Erasure is accomplished using an UV (Ultra Violet) light source that shines through a quartz erasing window in the EPROM package.
EEPROM (Electrically Erasable Programmable Read Only Memory) is similar to an EPROM but the erasure is accomplished using an electric field instead of an UV light source. This eliminates the need of a window. Usually, EEPROM refers to a device that requires a programmer or special voltage to program it.