Computers are not complicated. You just have to be willing to learn about them. And knowing about them starts with knowing their parts. So I am going to talk about the PCI and PCI express cards and why they are important for your computer. Without them (especially the PCI slot) it would be very difficult to expand and add on to your computer and the motherboard. Thus it is important to know about these two technologies.
The meat
Currently the most common use for PCI express is video. It is the slot on the motherboard were the video card is attached. If the on-board or built in vga cord input on your motherboard stops working, you would buy a new video card and insert it into your PCI express slot. The slot is usually a different color from the PCI slot.
On the other hand the PCI slot is used for more expansions because motherboards come with more of these slots. With the PCI express slot, you may get two slots whereas with the PCI slot you may see three, four and even more on a given motherboard.
The PCI slot is used to expand on Ethernet, sound card, modem, USB ports and other attachments you may wish to add to your computer. What this means is if the USB ports on the motherboard stops working you can buy a USB PCI card and insert it inside your computers PCI slot instead.
The physical difference between these two cards is the distant between the metal bracket and the start of the connector. A performance difference is that the PCI express slot is much faster than a PCI slot. That is why it is called a PCI express. It delivers a higher video performance than a regular PCI card.
In some cases the PCI express slot has its own (usually 4 pin) power connector that gives it the power it needs. However, most PCI express cards don’t use it.
Ending
Although these technologies have been around for a long time and improvements have been made in many areas of computing, the PCI and PCI express have not seen much change. The move from AGP(accelerated graphics ports) video format has taken and continues to take a long time. PCI apart from USBs continue to provide the main method of expansion. As far as PCI express is concerned, will we see expansions in the format for modems, network cards, raid cards etc in the near future?