According to PC Mag, ROM BIOS refers to the memory chip used on early PCs to store the software necessary to boot the computer. Newer PCs use flash memory for this purpose.
ROM is short for Read Only Memory. The data on this type of memory is unchangeable. In order to replace or update the data, it is necessary to physically remove the chip and replace it with another chip containing the new or updated data. This makes ROM chips more secure than flash memory. Video game cartridges also make use of ROM chips. Many microcontrollers make use of ROM chips and chip banks to store control instructions for many different applications. The ROM chip is an inexpensive method of storing data for use in any CMOS chip.
BIOS (Basic Input Output System) is the set of instructions used to boot a computer. These routines provide basic drivers for peripherals such as the keyboard, monitor and mouse. These drivers also provide the user with a way to edit or alter configuration settings. Prior to loading the operating system, these routines test the system and assign resources to all the devices connected to the motherboard. After the basic routines finish, the operating system takes control from the BIOS using more complex drivers. BIOS instructions are typically stored in flash memory to permit an easy method of replacing or updating the BIOS routines in newer computers.