Computers have a main power supply unit but it is not possible to deliver power to all the components directly from it. Hence, power connectors are used to distribute the power from the main supply to various components like RAM, CPU, chipset, and expansion cards.
Some modern expansion cards like the high-end graphics cards require more power which can’t be provided by the main power connectors of the computer. So, these graphics cards come with their own power connectors to get the right amount of electrical power.
Motherboards also have Flash ROM which a non-volatile memory chip uses to store the BIOS of the system. Apart from these, additional components like the USB (Universal Service Bus), disk controllers, Ethernet controllers, etc. exist on the motherboard. Modern motherboards also have on-board graphics chips (like Intel HD Graphics) and sound cards which are directly soldered on them. The internal graphics cards are capable of handling the basic graphics processing of the machine and provide video output through VGA and HDMI ports.