Understanding Motherboard Diagrams
Now that you have a diagram or manual for your specific motherboard, you need to note some important info about motherboard wiring. Check out the below picture to see a basic motherboard wiring diagram from Gigabyte. Also, here is an example of a full motherboard manual, which you should check out, as manuals are more common than diagrams.
As you can see from the above picture, a motherboard diagram is basically a blueprint view of the motherboard, with each connection port labeled. This comes in extremely handy for first time custom PC builders, as it details where each component is located on the board. Rather than having to manually identify each connection type, you can simply consult your motherboard manual to see which part goes where. As noted above, a full motherboard manual is much more detailed than a motherboard diagram alone. Often times, motherboard manuals even have instructions for installing each component, such as RAM, graphics cards, processor, etc...
Experienced PC builders may not need to consult a motherboard diagram at all. For the most part, each motherboard has the same basic expansion ports and connectivity options. Of course, some motherboards offer more advanced features than others, but the video card can only fit in one place, the RAM can only fit in one place, the CPU goes in the socket, and so on. Once you have this concept down, custom PC building becomes second nature.