Since most businesses use servers in a variety of different roles, it's a good idea to see just exactly what's inside. You will notice that server components are very similar to personal computer components. The major differences are the speed and the storage capacity of servers.
Motherboard. The motherboard of a server is similar to a PC's motherboard. As in a PC, the motherboard is what brings many of the other components together. Think of it as the body of the server. Most of the other components and electronic circuitry attach to the motherboard. Memory, a hard drive controller, input / output ports, and the chipset is all part of the server motherboard. Motherboards can also provide housing for components such graphic adapter and a network interface. Many of today's modern computers come with this circuitry built-in to the motherboard. When a motherboard fails, the system itself will fail.
Processor. The second major component is the processor or the central processing unit (CPU). This component, oddly enough, processes the data that crosses through its componentry. Think of a processor as the brains of the server. It is the component that largely affects system performance, though there are other components that contribute to its success.
Memory. This is the component that you should always have more than enough of. In fact, it was Bill Gate who famously said that you should only need 720kb of RAM (memory). We're into gigabytes now. Put a lot of money into memory because it will be money well spent.
Hard Drive. This is where you'll store everything. Again, you should get one that will suit your needs for years to come. Hard drive memory is cheap.
Video card. This is perhaps the one component that is significantly different from the PC. Servers do not have much use for sophisticated graphics cards. Go generic on this item.
Network connections. Network adapters are often built into the motherboard. You will still need to understand this component for it is through the connections that the other PC are able to connect. Otherwise, it's an expensive box with a lot of fancy components and gadgetry inside.
Power Supply This is mentioned (whereas wiring or soldering is not) because you will be using significantly more power than you would normally use with a PC. The number of hard drives that are housed inside the box will determine how large your power supply should be.