The motherboard is the most important part of a personal computer. It holds the central processing unit (CPU) or processor, memory chips including random access memory (RAM) and read-only memory (ROM), and expansion slots for connecting peripherals like sound cards and network cards. RAM is used to run programs and process data temporarily, while ROM permanently stores the basic input/output instructions a computer needs to boot. Common processor chips placed on the motherboard include the Pentium and PowerPC.