Electronically Erasable, Programmable Read-Only Memory. You can erase it one byte at a time, unlike Flash EEPROM, which lets you erase whole blocks at a time. It's a type of PROM, or Programmable Read-Only Memory. Those PROMs which were not erasable&electronically often needed strange things to reset them - such as bursts of radiation on specific light wavelengths. For more information, see the Dark Ages.