The word modem is actually short for Modulator/Demodulator. A modem is a communications device that can be either internal or external to your computer. It allows a computer to connect to the internet and transfer data through telephone lines. The original dial-up modems are becoming obsolete because of their slow speeds and are being replaced by the much faster cable and DSL modems.

Also known as the MB, Main Board or System Board. Basically, the motherboard is what connects everything in your computer together. The Motherboard is a printed circuit that is the foundation of a computer and is were all the internal components such as CPU, RAM, expansion slots, PCI slots, serial ports, USB ports, and all the controllers for things like the hard drive, DVD drive, keyboard, and mouse are all connected.

Sometimes referred to PSU(Power Supply Unit). The power supply is just that, an internal hardware component used to supply the computer with power/electricity.