BIOS software is stored on a non-volatile ROM chip on the motherboard. … In modern computer systems, the BIOS contents are stored on a flash memory chip so that the contents can be rewritten without removing the chip from the motherboard. This allows BIOS software to be easily upgraded to add new features or fix bugs, but can make the computer vulnerable to BIOS rootkits.
Since ROM means Read-Only Memory, why can the BIOS contents be rewritten?
Does the "flash memory chip" mean the same as the "non-volatile ROM", both meaning where BIOS is stored?