If you're talking about functions that were once available only by add-in cards, that's different. Many functions that require add-in cards are now integrated into the motherboard and these include sound, network capability and sometimes graphics. With the majority of boards today, you need only RAM memory and a CPU to make it functional. CPUs are increasingly adding graphics capability of the type suitable for everyday use. If you want more graphics power, you buy an add-in card. If you want to expand such things as are already on motherboard like extra USB ports or specialty ports, you get an add-in card.
I recently started studying computer's hardware, and I have a question. I've always thought, that expansion cards are mandatory ,and if you don't have a sound card, there simply will be no sound, but I read an article, that says, that every modern motherboard has built-in sound, video, network cards etc. It sounds a bit strange to me. I thought, that motherboard is just a printed-circuit board or at least PCB with slots, chips etc. like BIOS, ROM, CMOS etc., and that's why it can't possibly have every card already built-in. So, my questions are:
1) Does every motherboard have all built-in cards? Or there are cards that never come with a motherboard and you have to set them up separately?
2) What cards usually are built-in in the first place?
I really appreciate your help!