BIOS configuration changes are saved to nonvolatile BIOS memory which is usually flash memory that’s on the motherboard. Before flash memory, BIOS configurations were stored on a complementary metal-oxide semiconductor (CMOS). CMOS allowed you to write and then change BIOS configurations on the CMOS. A battery on the motherboard made sure the BIOS configuration information was constantly refreshed so the BIOS configuration wasn’t lost. With modern flash memory, we no longer need a battery to constantly maintain the information.
The CMOS battery is still included on modern motherboards even though it is not needed for flash based storage. It’s there to mostly maintain the date and time on the computer. If the battery dies and your remove the computer from power, you’ll notice that you need to change the date and time configuration every time you boot up your computer.
In legacy CMOS BIOS systems, you could reset the BIOS configuration simply by removing the CMOS battery. In modern computers, you’ll need to use a jumper to reset the BIOS settings.