SRAM (pronounced "s-ram") retains data by using an alternative source of power such as a battery. SRAM is often used to store computer hardware settings that need to be maintained when the computer is shut down. Common examples include the BIOS settings on Windows computers or the PRAM settings on Macintosh systems. Since SRAM typically uses a battery to retain memory, if the battery dies or is disconnected, the data stored in the SRAM will be lost. Therefore, if BIOS or PRAM settings are not retained after a computer is restarted, it is likely the computer's battery has lost its charge and needs to be replaced.
EEPROM (pronounced "e-e-p-rom") stores data using electrical charges that maintain their state without electrical power. Therefore, EEPROM does not need a battery or other power source to retain data. The most common type of EEPROM is flash memory, which is used for USB keychain drives and other portable electronic devices.