What is flash ROM

RAM sticks = volatile memory, the information stored in them disappears every time you turn off the PC

ROM or BIOS is the chip that keeps your PC's configuration in memory
what processor you have, what disk, etc.

ROM = read-only memory = BIOS
flashing the BIOS refers to updating it with a small program that you can download from the manufacturer's website for your motherboard.
To be avoided.